Category Archives: AML

acute myeloid leukemia

Updates from #CowenHealthCare 2020 – CAR T and it’s competitors

Aleta Biotherapeutics, ALL, AML, B cell lymphoma, B cell lymphomas, biologics, BITE bi-specific, cancer, CAR T, CAR T cells, Chimeric Antigen Receptor, chimeric antigen receptors, CNS pathologies, immunotherapy, leukemia, lymphoblastic leukemia, lymphoma, Lymphomas, Leukemias, Myelomas, myelofibrosis, , , , ,

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If you work in cell therapy you have follow all kinds of therapeutic developments in indications of interest which for us at Aleta Biotherapeutics (www.aletabio.com) includes specific solid tumor indications, and several hematologic malignancies.

Over the last few days we’ve gotten interesting updates regarding diverse hematologic malignancies, including news about therapeutics for front line (newly treated) or relapsed or refractory (r/r) Non-Hodgkin Lymphoma (NHL), multiple myeloma (MM) and acute myeloid leukemia (AML) patients and the myelodysplastic syndromes (MDS). Note here that the reference to different lines of therapy – front line or early line vs r/r, because the treatment paradigms change as patients fail earlier lines of therapy, ie. as they become refractory to or relapse from their current therapy. This can become a long and arduous battle for patients who repeatedly fail treatment. Unfortunately, this is often the case in r/r MM, r/r AML and MDS and in some subtypes of r/r NHL.

On Monday (2 March 2020) I attended the “Cell Therapy & Myeloma” panel at the 40th Annual Cowen Heath Care Conference. This panel covered much more than the title implies, and I really liked the format which is built on the back of questions posed to the audience, to an (unnamed) group of specialists in the field who were polled in advance, and to the seated key opinion leaders (KOLs), in this case Dr Deepu Madduri (Mt Sinai) and Dr Jacob Soumerai (MGH).

They covered a lot of ground.

The first series of questions sought to pin down trends in r/r Follicular lymphoma (FL) a subtype of NHL that can become difficult to treat if patients fail successive lines of treatment. The Leukemia Lymphoma Society has a primer here –https://lymphoma.org/aboutlymphoma/nhl/fl/relapsedfl/.  There has been brisk drug development in r/r NHL including FL. Novel drug classes include CAR-CD19 T cells, bispecific T cell engagers, small molecule drugs (targeting PI3K, Bcl2, BTK, EZH2) and new antibodies. The Cowen panel worked through a series of questions regarding this landscape and there were several key takeaways.

One was the clear preference, by the anonymously polled specialists and by the seated panelists, for CAR-CD19 therapy as the most exciting new drug for r/r FL. The driver here is the durability of response (DOR) in really late line patients and the sense that both overall response rate (ORR) and DOR will only improve as these cell therapeutics move to earlier lines of therapy. It was striking that several classes of bispecific antibodies (the CD3 x CD20 and CD3 x CD19 bispecifics) elicited strong enthusiasm from the audience (mostly analysts and investors) but only muted enthusiasm from the KOLs. This lack of enthusiasm had 2 distinct bases: 1) limited data to date, and 2) “I can give a bispecific after I give a CAR T, but not the other way around”, which was a very interesting thought (and given despite of the few case reports of CD3 x CD20 bispecific therapy working in several relapsed CAR-T patients). I think that in later line patients these clinicians want to keep their options open as long as possible.

Among the other classes of therapeutics, Epizyme’s EZH2 inhibitor tazemetostat received significant support based on the ability to select EZH2-mutated patients, and on good DOR and on good tolerability, the latter thought to be better than the PI3Kdelta class inhibitors, BTK inhibitors or BCl2 inhibition. The consensus was that tazemetostat could see up to 20% market penetration in third line FL after the expected launch in June 2020.

Among the PI3Kdelta inhibitors, Bayer’s copanlisib was singled out as best-in-class with little differentiation among the others (from Gilead, Verastem, MEI, Incyte, or TG Therapeutics). Finally, in this setting of r/r FL, both venetoclax (a Bcl2-inhibitor) and polatuzumab vedotin (a CD79b antibody-drug conjugate), were relegated to minor use by the specialists and panelists.

The uptake of CAR-CD19 therapies has been brisk, and the panelists highlighted quicker payor approvals and the accelerating pace of referrals to cell therapy centers. The consensus is for 30% increase in patient number treated in 2020 (so roughly 1350 patients in the US, vs 1050 treated last year).

The discussion stayed on CAR-CD19 therapeutics to touch on some of the newer trials and entrants. Kite/Gilead is running a Phase III trial of axi-cel (axicabtagene ciloleucel, brand name Yescarta) in second line DLBCL patients vs a standard of care regimen of high dose chemotherapy followed by an autologous stem cell transplant. Data are anticipated in the second half of 2020. The Cowen moderators passed the question: will this trial show a progression free survival (PSF) benefit?  Mind you, this is a low bar since overall survival – the shining triumph of cell therapy – is not part of the question. The audience (again, mainly investors and analysts) was overwhelming positive, giving about 70% odds of a positive impact on PFS. Here the panelists agreed, citing the fact that this trial was enrolling high-risk patients and therefore the comparator arm of the trial (chemo + ASCT) should do very poorly. Success with this trial would move axi-cel up a line of therapy (from 3rd or later to 2nd or later) and bolster the health care value argument that patients may avoid ASCT altogether.  We are apparently already seeing this effect, as a talk at #TCMT20 highlighted the steep decline in transplants being done in DLBCL.

Sticking with axi-cel, this CAR-CD19 cell therapy was highlighted as the one most likely to be the market leader by 2023, based on the (currently) much shorter manufacturing and turnaround time as compared to tisa-cel (tisagenlecleucel from Novartis, brand name Kymriah). The panelists agreed with the specialist poll, despite the fact that they also felt that tisa-cel may be better tolerated by patients overall. Further, the panelists did note that the difference in manufacturing turnaround was likely to diminish as Novartis improves its product workflow. So we’ll have to wait and see.

Competition may also play a role.  The long-awaited Juno > Celgene > BristolMyers Squibb CAR-CD19 liso-cel (lisocabtagene maraleucel) should see its first approval soon, and several allogeneic and non-T cell based programs are advancing. Cowen’s moderators highlighted a number of these for discussion. Allogene CAR-CD19, called ALLO-501 is currently in a Phase 1 trial enrolling r/r diffuse large B cell lymphoma (DLBCL) and r/r FL patients, with initial data expected later this year. The moderators put forward the question: what percent of (responding) patients have to show a durable response for this to be an exciting option to the autologous CAR-CD19 products. It’s a complex question since the current approved CAR-CD19s show about a 50% durable response rate within the responders, where a goodly proportion of the patients that do not have a durable response are relapsing after a response, sometimes with CD19-negative lymphoma or leukemia (ie. the cancer has undergone natural selection and loses target antigen expression). The polled specialists and the panelists wanted to see a pretty high durable response rate, 35-40% (specialists) up to 50% (the panelists). If the field were to see responses as good as axi-cel, tisa-cel and liso-cel, this would be “a huge advance”, according to Dr Soumerai of MGH.

Of note, Allogene itself was a bit more cautious at their public company presentation later in the day. Dr David Chang, Allogene’s CEO, provided some guidance and set expectations. He noted that the company would report early data form the ALLO-501 program at #ASCO20 and/or #EHA20 but stressed the readouts of safety and degree of lymphodepletion from up to 3 dose cohorts, and with several different doses of their lymphodepletion agent ALLO-647, and anti-CD52 antibody. In the ALLO-501 trial this is given along with the lymphodepeleting chemotherapy combination of cyclophosphamide and fludarabine (Cy-Flu). Among the other allogeneic and off-the-shelf CAR-CD19 programs several were highlighted either by the audience (Fate Therapeutics induced CAR-NKs) or the panelists (the Takeda/MD Anderson NK program). Other programs from Atara, CRISPR, and Precision all would have to show some or more data in order to get the specialists or the panelists to take notice.

Notably, there was consensus among the audience, polled specialists and panelists that CD3 x CD20 bispecifics would be less efficacious than CAR T cells, regardless of the specific therapeutics (eg. from Roche or Regeneron or Genmab). Further, Dr Madduri expressed concern at the need to keep dosing patients both because of inconvenience and possible safety over time. Her view is that patients prefer a single dose CAR.

Finally in the r/r DLBCL space, both polled specialists and the panelists saw minimal roles for the anti-CD79b-drug conjugate polatuzumab vedotin (brand name Polivy, from Roche) or the anti-CD19-ADCC competent antibody tafasitamab (from Morphosys, which now has a 30 August PDUFA date with FDA).  Both of these biologics need to be given in combination with other therapeutics and there did not appear to be a benefit over standard combinations. More specifically, polatuzumab vedotin is given with rituximab and bendamustine and was considered “tolerable” but perhaps best used in a bridge to transplantation setting or a bridge to CAR-CD19 cell therapy. Tafasitamab was recently written up by Jabob Plieth here: https://www.evaluate.com/vantage/articles/analysis/why-2020-spotlight-will-fall-tafasitamab.

Turning to r/r MM there were a series of questions about lines of therapy and which were preferred. For newly diagnosed patients and for second-line patients the clearly favored standard of care was an ‘ImID’ (immunomodulatory agent, eg. revlimid) plus the anti-CD38 antibody daratumumab (brand name Darzalex, from Johnson & Johnson’s Janssen division) plus dexamethasone (aka triple therapy) with perhaps a proteasome inhibitor added (thus, a quad). The use of daratumumab in early line therapy will continue to grow as it is payor-approved for early-line use.

For later line therapy, the moderators first brought up selinexor (brand name Xpovio, from Karyopharm Therapeutics), a first-in-class, oral Selective Inhibitor of Nuclear Export (SINE), which was granted accelerated approval last year for use in in combination with dexamethasone for adult r/r MM patients who received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two ImIDs, and an anti-CD38 monoclonal antibody. There was a consensus view that this drug will see flat to diminishing use due to poor tolerability. Dr Madduri noted that she gives this drug once week rather than twice a day (as labeled) in an effort to improve patient tolerance and only used it as a bridge to clinical trial enrollment (ie. on something else, for example, CAR-BCMA cellular therapy. Curiously there were no questions about isatuximab-irfc (brand name Sarclisa, from Sanofi-Aventis), newly approved in combination with pomalidomide and dexamethasone for adult patients with r/r/ MM and at least two prior therapies (see this SITC writeup: https://www.sitcancer.org/aboutsitc/press-releases/2020/isatuximab-irfc).

As for CAR T cells for multiple myeloma, the panelists were hesitant to pick a winner between the two advanced CAR-BCMA programs: bb2121 (Bluebird) and JNJ-4528 (from J&J, formally called LCAR-B38M) until J&J updated PFS data. At their public company presentation Nick Leschly, Bluebird’s CEO, noted that they will file the BLA for bb2121 (now called idecabtagene vicleucel or ide-cel) in the first half of this year, and would release longer-term follow-up data from the ide-cel clinical trials KarMMa and CRB-401 in the second half of the year. The BLA will be filed despite the “slow-down” from FDA necessitated by the agency’s request for additional lentivirus production characterization information from their chosen cell suspension manufacturing method (no details given). What the FDA has asked for apparently is both different from and more than the EU agency (EMA) wanted.

On the allogeneic CAR T cell front, Dr Chang at Allogene noted that they would have early data on ALLO-715 (their version of a CAR-BCMA therapy) at #ASH20. Here he noted they are considering dropping the Cy-Flu lymphodepletion and just using their anti-CD52 antibody to lymphodeplete, we’ll see (this doesn’t strike me as realistic).

In general both the polled specialists and the panelists were more enthusiastic about CAR-BCMA therapy than several other modalities, including belantamab mafodotin (from GSK), an antibody-drug conjugate, composed of an anti-BCMA monoclonal antibody bound to auristatin F. This drug was thought to be not quite good enough given the unmet need, there remain concerns about the ocular toxicity (the bane of ADC technology) and keen disappointment that the response rate dropped below 30% ORR in daratumumab-refractory patients. Clearly this therapeutic will see some use in late line therapy, and further clinical development has yielded results in earlier line as reported on 2 March (see https://www.evaluate.com/vantage/articles/news/trial-results/karyopharm-comes-boston-springtime). A similar wait-and-see approach is being taken by these specialists and panelists to the CD3 x BCMA bispecifics, which are currently viewed as best for community hospital settings without CAR T cell capacity or for patients who cannot wait for the cell therapy production.

One theme in r/r MM is the concern that patients are still not being cured, even with cell therapies. The gradual relapse from CAR-BCMA treatment that one sees in all the clinical studies has been linked either to CAR T persistence being limited or to diminished BCMA antigen expression on the cancer cells. Of course, these two things may be related. One desire expressed by Dr Madduri was for a CAR-BCMA therapy with better persistence properties.

Two short notes while we’re here. Gilead stated at their public company presentation during Cowen Health Care that the value driver for the Forty Seven acquisition was the MDS data (https://xconomy.com/san-francisco/2020/03/02/gilead-boosts-cancer-drug-pipeline-with-4-9b-deal-for-forty-seven/). And hematologic drug heavyweight venetoclax (the Bcl-2 inhibitor from Abbvie) scored a miss in an AML confirmatory trial (https//pharmaphorum.com/news/abbvie-roches-venclexta-fails-in-confirmatory-aml-trial/). In summary, a busy couple of days.

As many readers know, Aleta Biotherapeutics builds cellular therapeutics with exemplary persistence and fitness properties. We have two cell therapy programs heading for the clinic now. One will treat r/r AML patients both in the pediatric and adult patient populations. Our solid tumor program is designed to treat patients relapsing from breast or lung cancer with brain metastases. We also have a biologics program specifically created to ‘rescue’ CAR-CD19 T cells in patients relapsing from therapy. You can find out more at www.aletabio.com or email me at paul.rennert@aletabio.com or just call me at 1-508-282-6370 and of course follow me on Twitter @PDRennert and @BioAleta.

That’s it for now.  Stay tuned.

The French Connection – Lirilumab Edition

AML, Bristol Myers Squibb, immunotherapy, Innate Pharma, lirilumab, Lymphomas, Leukemias, Myelomas, monoclonal antibodies, oncology, PD-1

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Bristol-Myers Squibb (BMS) has quietly changed the protocol of clinical trial NCT01592370. This Phase 1 clinical trial has evolved from a nivolumab (anti-PD-1) study in hematological malignancies (5/4/14) to include ipilimumab (anti-CTLA4) with nivolumab (4/8/14) to now include nivolumab, ipilimumab and lirilumab (anti-KIR) as of 10/30/14. The changes were noted on Twitter (where else?) by several biotech experts who posted this screen shot:

Screen Shot 2014-11-02 at 7.04.24 AM

The striking thing to notice is the addition of lirilumab across the board.

The clinical trial includes the following indications/inclusion criteria:

  • Subjects must have histological confirmation of relapsed or refractory hematologic malignancy
  • Subjects with non-Hodgkin’s lymphoma or Hodgkin lymphoma must have at least one measureable lesion >1.5 cm as defined by lymphoma response criteria. Tumor sites that are considered measureable must not have received prior radiation therapy
  • Subjects with Multiple Myeloma (MM) must have detectable disease as measured by presence of monoclonal immunoglobulin protein in a serum electrophoresis: IgG, IgA, IgM,(M-protein ≥0.5 g/dl or serum IgD M-protein ≥0.05 g/dl) or serum free-light chain or 24 hour urine with free light chain. Excluded are subjects with only plasmacytomas, plasma cell leukemia, or non-secretory myeloma
  • Subjects with Chronic myelogenous leukemia (CML) must have evidence of the Philadelphia chromosome by polymerase chain reaction (PCR) or chromosome analysis
  • Life expectancy of at least 3 months
  • For subjects with lymphoma, either an archived Formalin fixed tissue block, or 7 to 15 slides of tumor sample for performance of correlative studies
  • Subjects must have received at least one prior chemotherapy regimen. Subjects must be off therapy for at least 3 weeks (2 weeks for oral agents) prior to Day 1

The trial covers Non-Hodgkin Lymphomas (NHL), Hodgkin Lymphoma (HL), Multiple Myeloma (MM), Acute Myelogenous Leukemia (AML), a subset of Chronic Myelogenous Leukemia (CML) and other hematologic malignancies. The requirement for biopsy tissue is to support biomarker analyses.

Lirilumab is an antibody developed by Innate Pharma (IPH.PA) that binds to the KIR2DL1, -2, and -3 receptors and prevents them from binding to HLA-C. HLA-C is a B2-microglobulin bound MHC family member with antigen presenting function. As an ancient system of antigen presentation, HLA-C is expressed on virtually all cell types. Binding of HLA-C to KIR2DL isoforms induces an inhibitory signal that prevents NK cells from engaging in cytotoxic control of tumors. By preventing KIR-mediated suppression of NK cells, lirilumab increases NK cell–mediated killing of HLA- C+ tumor cells.

Lirilumab showed signs of clinical activity in a Phase 1 trial and acceptable toxicity was observed (Vey et al. 2012. Blood 120: 4317, Vey et al. 2013. Blood. 122: 21, abstracts). A Phase II study of lirilumab in AML is in progress and combination Phase 1 trials of lirilumab in combination with ipilimumab and nivolumab for a variety of tumor types have begun. Lirilumab is also being tested in combination with the depleting antibody elotuzumab (anti-CS1) in refractory MM. The lirilumab-titled trials are listed below:

Screen Shot 2014-11-02 at 7.51.28 AM

So what to make of all this activity? One reasonable conclusion is that enough data from interim analyses of the AML trials has come in to convince BMS to double-down on the partnership with IPH and move lirilumab forward aggressively. The breadth of indications is impressive. A second, related, conclusion is that preliminary data on lirilumab’s clinical activity in AML is ready for presentation at the American Society of Hematologists (ASH) Conference in December. The abstracts from that conference will come out on November 6th, so we’ll see.

There is considerable interest in combining T cell directed immune checkpoint therapeutics with those that act on NK cells. Innate Pharma (IPH.PA) has additional programs of interest in the NK cell space, including an antibody that targets MICA, a negative regulator of NKG2D-mediated activation of NK cells and an antibody that targets NKG2A, an inhibitory receptor.

The focus of this company on NK cell biology is impressive and may finally drive strong valuation. Innate has some very vocal supporters, but many investors seem reluctant to back this company. One reason perhaps is that it trades in Europe and liquidity of the corresponding US shares (OTC:IPHYF) is low. Another reason is perhaps the relationship with Novo Nordisk, which owns about 15% of company equity. From the scientific perspective the company is innovative and exciting, and I would love to have someone explain the stock valuation issues. Innate raised significant capital earlier this year with a round led by Orbimed, Redmile, FMR and about a dozen other top tier investors. An early look at AML results for ASH, or perhaps at ASCO, and strong clinical data thereafter could make many retail and institutional investors happy.

stay tuned

Kites Fly: Effective CAR-T Therapy in Non-Hodgkin Lymphoma? Hematological Malignancies Part 4

ALL, AML, B cell lymphoma, B cell lymphomas, CAR-T, chimeric antigen receptors, immunotherapy, Kite Pharma, lymphoblastic leukemia, Lymphomas, Leukemias, Myelomas, monoclonal antibodies

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Sorry for the slight delay getting this out. I was trying to account for each patient as even 1 or 2 misplaced will impact the response numbers in these small trials. Took a while.

Our last post focused on the CAR technology coming out of the MSKCC and affiliated institutions, being brought together under the Juno company umbrella. Juno was funded by ARCH Venture Partners and the Alaska Permanent Fund, through a partnership managed by Crestline Investors, along with Bezos Expeditions, and Venrock. We noted in closing that CAR T cell technologies were performing very well in acute lymphocytic leukemia (ALL), but not as well in the Non-Hodgkin Lymphomas (NHL). In early data sets response rates were not trending very high.

Recently I came across Kite Pharma’s JPM update on their version of CAR therapy. Kite is financed by Pontifax Ltd., Alta Partners, Commercial Street Capital, and individual investors, in partnership with the National Cancer Institute (NCI) Surgery Branch under a Cooperative Research and Development Agreement (CRADA). This reflects that the technology is coming out of NCI labs.

I was struck again by the duration and response rates reported and the indications they were pursuing. It seems that there is one extra patient in the JPM slide deck, so I went back to the ASH talk to get the right numbers. So lets review. Kite calls its lead CAR construct a very straightforward name: anti-CD19 CAR. Like 19-28z CAR from Juno/MSKCC, this CAR is built with a anti-CD19 scFv, followed by CD28 and CD3 signaling components. Quite unlike the 19-28z effort however, the lead here is NHL indications, specifically as seen here:

Screen Shot 2014-03-26 at 5.28.38 PM

Click to read the full blog post →

Some ideas from Macrogenics: B7-H3, DARTs, ADCs and more

ADC, AML, BITE bi-specific, DART bi-specific, immunotherapy, Macrogenics, monoclonal antibodies

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Screen Shot 2014-03-10 at 12.54.13 PM

Macrogenics is a very interesting company whose next 2 or 3 years will surely determine its’ future. And it’s probably about time, as the company has 14 years under its belt. The company is public and trades on NASDAQ as MGNX.

We’ve watched many companies approach a critical time horizon, when possible futures begin appearing. Some companies become great, others wither away, but it is no longer possible to tread water. Macrogenics knows this well, and they are aggressively working to carve a successful path forward. CEO Scott Koenig and CFO James Karrels rang me up the other day, spending about an hour giving me a look under the hood. Our discussion was part history lesson, part update and all very interesting. What follows is just my personal opinion about what we discussed. I’ve tried to place my thoughts in the larger context of the antibody and immunotherapy landscape in the treatment of cancer.

The Macrogenics’ story includes an enhanced Fc technology for cytotoxic antibodies, a bi-specific antibody technology known as DART (see below), a series of partnerships with pharmaceutical companies, and some new initiatives. I’m not going to discuss the past type 1 diabetes effort and the teplizumab antibody as that story is well known.

Lets start with a very interesting program that has been built around the HER2 enhanced Fc antibody, margetuximab. Results from the Phase 1 trial were presented at ASCO last year, and there were early signs of therapeutic activity. The early data showed activity at doses ranging from 1-6 mg/kg qw and 10 mg/kg q3w. This is in the dose range already used for Herceptintm (trastuzumab; 4mg/kg qw or 8mg/kg q3w) and Kadcylatm (trastuzumab emtansine; 3.6 mg/kg q3w). Macrogenics’ hopes that margetuximab can eliminate cancer cells expressing lower levels of Her2 than tumors addressable by trastuzumab (which targets Her2 high expressing cancer cells). Program success hinges on this hypothesis.

Macrogenics is aggressively moving this antibody into Phase 2 and 3 programs including breast, bladder and gastroesophageal cancers with relatively low expression of Her2. The planned phase 3 trial of margetuximab plus chemotherapy in gastroesophageal cancer should start by the end of this year. A phase 2a trial in metastatic breast cancer should wrap up in the second half of this year, and we should see data in 2015. This is important because in the absence of compelling clinical data it will remain difficult for this program to drive further valuation. This is because the Her2 space is very crowded, and it may be hard to establish differentiation and gain leverage. The broad attack against diverse cancer types therefore makes sense. So while I like this program it is going to require compelling phase 2 data to really generate buzz.

The other day I wrote about immune-checkpoint programs         (http://www.sugarconebiotech.com/?p=522) and in this area Macrogenics has nicely positioned its Fc-enhanced anti-B7-H3 antibody MGA-271. This first-in-class program is optioned to Servier, and has advanced to Phase 1 in solid tumors. The company was lucky to pick up this antibody target when it acquired Raven. It is one of a number of B7 family proteins with ill-defined biology. Importantly, Macrogenics focused on the expression pattern of this protein, that is, they treated it as a cell surface target and not as a biology target. This turned out to be a smart move, as this protein is highly and preferentially expressed on a wide variety of tumor cells, and Macrogenics is going after this antigen with a cytotoxic antibody. This type of immune targeting antibody is well positioned for combination with other therapies that “unleash” immune cell responses, particularly the NK cell and macrophage release strategies. We talked about a few of these last week (http://www.sugarconebiotech.com/?p=524). This program looks very interesting and has nothing but upside assuming we do not see a toxicity signal as the clinical trials move forward.

Macrogenics is smartly building out this space. Scott and Jim explained that some of the money recently raised in their stock offering is going to support best-in-class antibody process and manufacturing, and that this will include antibody-drug-conjugates (ADCs), which are toxin payloaded antibodies. Importantly, DARTs directed to appropriate targets will internalize – a prequisite for good ADC-mediated cell death. I asked them if they had chosen a partner for the ADC work (like Seattle Genetics or Immunogen) and they hedged just a bit, saying that different linker-payload combinations might be employed for different antibodies and targets. That’s certainly a reasonable approach, if heavy on the downstream process and formulation steps, so we’ll see what they decide.

An important part of the Macrogenics portfolio is certainly the DART technology. DART is an acronym of Dual Affinity ReTargeting (or Redirected T-cell), depending on the compound. So, there are a couple of different plays here. One is a T cell engagement technology. The furthest developed technology in this class is Micromet/Amgen’s Bi-specific T-cell Engager (BiTE). The CD3 x CD19 BiTE, blinatumamab, recruits T-cells through CD3 and directs them to kill CD19 positive cancer cells. Blinatumamab is reportedly active at concentrations of 100pg/ml or less and certainly in some leukemia settings induces very impressive and durable therapeutic responses, although the side effect profile includes CNS toxicity, including encephalopathy. We will talk much more about the BiTE technology in the next post.

I asked Scott and Jim about the encephalopathy toxicity, specifically whether this is a class effect due to T cell activation. Scott pointed to the way Micromet BiTEs are constructed, and the “floppiness” of the two arms, suggesting that this could have a different impact on a responding T cell than the covalently “locked” DART construct. A second point is that this could be a toxicity that is only seen with the CD19 x CD3 bi-specific and not other bi-specifics. Scott mentioned that similar toxicity has been seen in the setting of CAR-T CD19-directed therapy (CAR19). Honestly, we can’t really judge at this point and will have to await clinical results before we actually know the efficacy/toxicity profiles of various T cell recruitment and activation technologies will compare.

Preclinically, Macrogenics has done a nice job of differentiating itself from BiTEs. In an in vitro study comparing CD19 x CD3 bi-specific formats using the DART technology and the BiTE technology the DART compound was active at much lower concentrations, including against patient derived chronic lymphocytic leukemia cells       (http://bloodjournal.hematologylibrary.org/content/117/17/4403.full). This may not matter so much just yet, as Macrogenics has chosen different bi-specific pairings, and for the moment will not compete directly with the CD3 x CD19 modalities, whether blinatumamab or CAR19.

Macrogenics DART technology has been validated in the partnership space. Boehringer Ingelheim (BI), Servier, Pfizer, and Gilead have all bought into the DART story with partnership deals. BI signed for up to 10 targets across diverse therapeutic areas and modalities and recently choose a DART compound to advance into preclinical development. Pfizer also signed a DART technology deal in 2010 for two cancer targets. Most recently, Gilead acquired rights to four pre-clinical DART programs for cancer indications. Gilead will fully fund research activities for all four programs and will receive global rights to three of the programs. Servier has rights to three DART programs and recently exercised an option to develop the MGD006 DART molecule in development for hematologic malignancies. This antibody is bispecific for CD123 (expressed on leukemias and lymphomas) and CD3 (expressed on T cells). Pre-clinical studies showed that the compound killed CD123-expressing leukemia cells at very low concentrations. A Phase 1 study in relapsed and refractory acute myeloid leukemia will start in the second quarter of 2014. This is the first study of a DART in the clinic.

So while this falls short of actual clinical success, the fact that diverse companies have lined up here is promising. Additional deals should be expected. Macrogenics also mentioned that they have an NK cell retargeting platform as well (one that would compete with the BiKE platform) and it will be interesting to see if deals are made on this technology as well.

Lets take a closer look at the DART targets.

The T cell engagement targets are CD123 (for MGD006) a target on acute myeloid leukemia (AML) cells, and gpA33 (for MGD007) a target on colorectal cancer cells. CD123 expression on AML is a target for ADCS, Bi-specific technologies, and CAR-T technology (CART123). So, this is an important target to understand.

CD123, a subunit of the IL-3 receptor, is over-expressed on AML tumor cells (and other hematopoietic tumor types). It is also expressed on normal hematopoietic stem cells, at a somewhat lower level. Recently, cancer stem cells (CSC) have been highlighted as sources of resistance to therapy. These are stem-like tumor cells that are very resistant to chemotherapy or irradiation, and are hypothesized to be a component of relapse in various tumor types. AML CSC are CD123 positive. Ideally then, therapeutics targeting CD123 will deplete AML tumor cells, deplete AML CSCs and hopefully not deplete normal cells. Because of the uniqueness of the CSC hypothesis, agents targeting CD123 and other CSC markers have gotten a lot of attention.

Lets start with CART123. Just a quick reminder, with CAR-T we are talking about the transduction of patient T cells with a modified TCR, a CD3 subunit and the 4-1BB signaling domain. Very nice preclinical data were presented at ASH last year by the group at The Children’s Hospital of Philadelphia         (https://ash.confex.com/ash/2013/webprogram/Paper60937.html) using technology that has been licensed to Novartis. However, there has been no further news on this target. Very recently, a second CAR-T/CD123 program was described by investigators in Italy and the UK (http://www.nature.com/leu/journal/vaop/ncurrent/abs/leu201462a.html). The preclinical data were compelling, and there did not seem to be an effect on normal cells. We’ll have much more on CAR-T technologies in a separate post.

Further along are competing anti-CD123 antibodies. Xencor developed two anti-CD123 antibodies that were then licensed to CSL limited. The first, CSL360, failed to show signs of clinical activity in a Phase 1 AML trial. The second, CSL362, had excellent cytotoxic activity in preclinical models and a Phase 1 trial in AML is recruiting. In December of 2013, CSL Limited licensed this program to Janssen/Johnson&Johnson. So, this program now has some real muscle behind it. An interesting note on the trial, it is being run in patients currently in remission. If I think this through I think this means the therapeutic hypothesis is two-fold. One, to drive the leukemia to MRD status (minimal residual disease = below the limit of detection); two, to eliminate CD123+ CSCs.

Stemline (NASDAQ: STML) has brought an anti-CD123-ADC antibody into the clinic. They had several presentations at ASH last year, including a phase 1 trial in Blastic Plasmacytoid Dendritic Cell Neoplasm, a rare cancer with high expression of CD123. They showed 5/5 patients responded, with 4/5 having a complete                     response (https://ash.confex.com/ash/2013/webprogram/Paper64672.html). This will be an interesting therapeutic to watch.

Macrogenics presented preclinical data on MGD006 at ASH         (https://ash.confex.com/ash/2013/webprogram/Paper55959.html).  As mentioned above the phase 1 study in AML will start later this year. A second CD123 x CD3 bispecific is being developed by the Cancer Research Institute at Scott & White Healthcare in Texas (they already have an IL-3 fusion protein). There is also a tri-specific targeting CD33, CD123 and CD16 (to activate NK cells). This has made it to the clinic (http://www.translational-medicine.com/content/11/1/289).

Gpa33 is an antigen that is highly overexpressed on colon cancer. This antigen was targeted a few years ago using a humanized anti-gpa33 monoclonal antibody. However the humanization effort did not work well and the therapeutic was highly immunogenic. As far as I can tell Macrogenics is alone in this space.

An earlier stage bi-specific technology at Macrogenics targets multiple antigens. Their CD32 x CD79 bispecific cross links these receptors on B cells and stops cell activation.

As discussed above much of the effort ongoing at Macrogenics is directed to their many partnerships. We do not know the targets for most of these, but one can imagine the direction that Gilead might take, or perhaps Pfizer. The deal with Servier is very interesting in the context of the Servier CAR-T technology deal. As reported in mid-February Servier will collaborate with Paris-based Cellectis on UCART19, an engineered T cell with a chimeric antigen receptor targeting CD19, plus 5 other programs all in leukemia and lymphoma. The company plans to develop combination therapies with immunotherapeutic monoclonal antibodies, small molecules, etc.

What we are seeing then is the co-development of bi-specific modalities directed to the same targets as CAR-T modalities, sometimes by the same company. This latter point is critical and fascinating. Could DARTs and BiTES compete not only with ADCs but also the CAR-T technologies? I don’t know, but we may find out in just a few more years. And we do have to be patient – Macrogenics has no clinical news scheduled until 2015. One way the company could make a splash is if it were to do something big on the corporate side – a buyout, merger, acquisition. Certainly their promotional deck (link here: http://bit.ly/1qpPQWL) makes the point on the last slides that Macrogenics is flexible as it has plenty of capital.

I really like this company – their technology is gutsy and innovative and I wish them the best. Now it’s time for clinical execution: the data will guide us from there. In the meantime there are a few really interesting ways to think about the technology opportunity and the underlying equity value.

cheers, and stay tuned for some thoughts about BiTEs, BiKEs, CARTs and KITEs.

AML Therapeutics Part 3: Immunotherapy

ADC, Amgen, AML, biologics, CAR-T, chimeric antigen receptors, Lymphomas, Leukemias, Myelomas, Merck, monoclonal antibodies, oncology, Onyx Pharma

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Ryan Teague and Justine Kline recently put together a nice review of immune evasion in acute myeloid leukemia (AML). The open access paper is available online (http://www.ncbi.nlm.nih.gov/pubmed/24353898). These authors have particular interest in tumor escape from immune surveillance by two interesting mechanisms. The first is termed T cell exhaustion, and refers to a non-responsive state induced in CD8+ (cytotoxic) T cells. The second is immune suppression, mediated by TGFbeta and regulatory T cells (Tregs). Other means used by tumor cells to avoid the immune system include deactivation by co-opting signals that directly shut down immune responses, such as PD-1 and other signaling mechanisms.

Why the interest in immunotherapy for such an aggressive cancer? There are a number of good reasons. First I think it is fair to state that targeted therapeutics (small molecule drugs) and antibodies (mAbs, ADCs, bispecifics) have yet to achieve a breakthrough in AML. The best of these drugs, even in combination, are only modestly effective. The second reason, implicitly recognized by the T cell engaging bispecific antibodies (BiTEs, DARTs) and by the still nascent CAR-T cell engineering technology, is that there is evidence to suggest that AML can be controlled by an effective immune response. This evidence comes from the leukemia transplantation field. As Teague and Kline state:

“Treatment with modern chemotherapy regimens often induces complete remission, but a majority of patients will ultimately relapse … it has been recognized that allogeneic stem cell transplantation can be curative for some patients with AML … derived from the so-called graft-versus-leukemia effect thought to result … Unfortunately, only a minority of patients with AML are candidates for this procedure.”

Those who are familiar with allogeneic SCT will further recognize that this is a risky procedure that can outright fail. So, are there safer or more direct ways to harness an anti-tumor immune response?

Novel therapeutics developed to stimulate anti-tumor immunity include the CTLA4 antagonist mAb, ipilimumab (Vervoytm; Bristol Myers Squibb (BMS)), approved for use in refractory or non-resectable melanoma. BMS is also developing the anti-PD1 mAb nivolumab, and combination trials with ipilimumab are underway. Other anti-PD1 and anti-PDL1 antibodies in advanced development for a variety of tumor types include MK-3475, submitted last month for FDA approval for the treatment of advanced melanoma, MPDL3280A (Roche), MEDI4736 (Astra Zeneca), and others. These are critically important therapeutics in hematological cancer and solid tumors. The potential breadth of applications is illustrated by the announcement last week the Merck will seek collaborative partnerships to develop MK-3475 in combination therapies. Merck will partner with Pfizer to investigate combination therapy in a phase 2 renal cell carcinoma (RCC) trial with the VEGFR inhibitor axitinib (Inlytatm). Merck will also partner with Pfizer for a phase 1 trial(s) using MK-3475 with the agonist anti-41BB antibody PF-2566, in multiple cancers. Readers will note that 41BB signaling is a critical component of the CAR-T T cell engineering technology. The collaboration with Incyte is also a dual-immunotherapy approach, as MK-3475 will be combined with INCB24360, an IDO inhibitor, in a phase 1 non-small cell lung cancer (NSCLC) trial. IDO is secreted by tumor cells, is a mediator of T regulatory T cell activity, and in AML is associated with poor prognosis. With Amgen, MK-3475 will be used in combination with the oncolytic viral therapeutic T-VEC, which induces tumor cell death and stimulates anti-tumor immunity.

The point of all this is to illustrate that for difficult cancers – melanoma, RCC, NSCLC – its not going to be easy, and combinations of novel therapeutics will have to be utilized. AML is a very difficult cancer. With this in mind we can look at the state of immunotherapy drug development in AML.

The Teague and Klein review goes into considerable detail on this subject, so we’ll just hit a few highlights and then see if we can update the storyline. A point the review makes that I didn’t fully appreciate is that AML tumor cells (and many others) can downregulate MHC Class I and II, making the tumor cells difficult for the immune system to recognize in the context of allogeneic SCT. This fundamental type of immune evasion may be difficult to circumvent. Other mechanisms of immune evasion used by AML include expression of PD-1L on the tumor cells, which effectively shuts down tumor infiltrating T cells that express PD-1, the PD-L1 receptor and mediator of a potent signaling response that downregulates T cell activity. AML tumor cells also express B7 family proteins B7-1 and B7-2,that bind to CTLA4, another downregulatory receptor. Clinical trials enrolling AML patients for treatment with therapeutics such as ipilimumab, nivolumab etc are described in the review. Its sufficient to point out that the effort to use these therapeutics for AML is in its very earliest stages.

A few recent observations point to other immune evasion strategies that night be productively targeted in AML.

Several preclinical studies have identified co-expression of TIM-3 and PD-1 as markers of CD8+ T cell “exhaustion”, and have likewise identified PD-L1 and galectin-9 (a putative TIM-3 ligand) on AML patient cells. TIM-3 is yet another receptor on T cells that mediates downregulation of T cell activity. Other markers of AML cells from patients were recently described (https://ash.confex.com/ash/2013/webprogram/Paper56968.html).

Relevant proteins included B7-2 (CD86), B7-H3 (CD276) and PD-L1. Patients with very high expression of both B7-2 and PD-L1 had worse overall and relapse free survival. HVEM, a receptor for several critical immune proteins including LIGHT, CD160, and BTLA, was expressed on a subtype of AML with relatively good prognosis. The author’s conclude ” that the profile of immune checkpoint molecules … correlates with molecular disease characteristics in AML and may even possess prognostic information, especially for relapse … (and) as therapeutic targets with respect to boosting anti-leukemic immune responses.”

An example of such an approach is provided by Innate Pharma, which is developing an anti-KIR antibody, lirilumab. KIR negatively regulates NK cell anti-tumor activity. A phase 1 trial in AML is continuing                             (https://ash.confex.com/ash/2013/webprogram/Paper59174.html). Preclinical data support the use of this mAb in combination with the cytotoxic anti-CD20 mAb rituximab in lymphoma. One might envision a similar approach using a cytotoxic mAb targeting AML such as the anti-CD33 mAbs discussed in part 2. Another possibility are the anti-CD38 mAbs. Second generation CD38 mAbs with improved cytotoxic activity are under intensive development for multiple myeloma by Sanofi (mAb SAR650984), Jannsen (daratumumab aka HuMax CD38) and MorphoSys (mAb MOR03087).

Another example is CoStim Pharma, bought today by Novartis. In their portfolio are novel immunotherapeutic mAbs, including TIM-3 antagonist mAbs. Novartis is moving quickly here to beef up its immunotherapeutic pipeline, which it can now develop in parallel with the U Penn CAR-T technology. Another local, private immunotherapy company is Jounce Therapeutics.

As we have also seen in parts 1 and 2, drug development for AML lags significantly behind other leukemias, lymphomas, myelomas, and the like. However, targeted therapeutics such as the tyrosine kinase inhibitor sorafenib, HDAC inhibitors vorinostat and panobinostat, and proteosome inhibitors bortezomib and carfilzomib hold some promise. The FLT3 and c-Kit targeting agents seem less likely to provide meaningful long-term benefit, although we’ll see what the combo trials brings. While it is too early to assess the CAR-T technology, the bispecific modalities, or immunotherapies in AML, the cytotoxic mAbs and ADCs should have a prominent role in controlling this aggressive disease.

We asked in Part 1 who the winners would be in 5 years. Looking over the landscape of therapeutics its pretty clear that winning will require collaboration among companies. With that said those companies with the biggest concentration of effort in AML include Merck, Onyx, Novartis, Amgen and perhaps Seattle Genetics. Given their past successes we can be hopeful that several of these companies will succeed in establishing breakthrough treatments for AML. In the end, patients should benefit the most from all of this activity. Perhaps stockholders will also benefit. With this in mind we note that Onyx probably has the most to gain (or lose) in this indication.

 stay tuned.

Anticipating new therapeutics and forecasting treatment trends for acute myeloid leukemia – Part 2

ADC, AML, biologics, CAR-T, chimeric antigen receptors, Companies - stock symbols, monoclonal antibodies

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Here is a quick recap of Part 1: we looked at some of the targeted small molecule drugs being developed for AML. That class of therapeutics can be binned into logical groups, as follows:

1) pan-signaling pathway inhibitors like sorafenib, sunitinib, even ponatinib

2) drugs that hit c-Kit (and various other receptor tyrosine kinases) like dasatinib and imatinib

3) drugs that target FLT3 (and usually hit other kinases) like quizartinib, midostaurin, lasartinib, and PLX3397

4) proteosome inhibitors like bortezomib and carfilzomib

5) epigenetic modulators like vorinostat, panobinostat, 5-azacitidine, decitabine and entinostat

6) miscellaneous. We discussed several of these in Part 1, and there are many more. One more of interest is AG-221 (Agios; AGIO) that targets the mutated IDH2 gene. IDH1 can also undergo mutation in AML. Such drugs are a nice idea, unlikely to work as monotherapy (just my view), but perhaps useful in combo. AG-221 is currently in early stage clinical development.

In the small molecule drug development landscape there is logic that is readily understandable, and the combinations of drugs being tried make good sense. In contrast the biologics side of AML drug development is pretty haphazard. On the other hand true breakthroughs leading to transformative changes in clinical practice very likely will be found here.

So lets move on to Part 2: Biologics, including cytotoxic monoclonal antibodies, ADCs, bi-specific antibodies, cell based therapy and few odds and ends.

An antibody that illustrates that haphazard nature of AML drug development is gentuzumab, a monoclonal antibody (mAb) directed to CD33, a protein expressed at high levels on AML cells. The mAb was coupled to a calicheamicin derivitive and developed as gentuzumab ozogamicin (GO). GO is therefore an antibody-drug conjugate (ADC). This drug was originally approved as Mylotargtm (Wyeth, now Pfizer; PFE) for the treatment of AML more than a decade ago based on a phase 2 trial data showing a CR + CRp rate of 30%. However the drug showed less benefit than expected in phase 3, plus unanticipated hepatic toxicity, and was pulled off market. GO continues to see use in clinical trials and off-label and has been shown to add to the effectiveness of chemo in AML patients carrying specific cytogenetic markers. A meta-analysis of large phase 3 trials was reported in the Annals of Oncology 2 weeks ago                           (http://annonc.oxfordjournals.org/content/25/2/455.abstract). Data from nearly 3600 patients (half treated, half controls) from five randomized phase 3 trials were analyzed. Compared with induction chemotherapy alone, adding GO significantly prolonged OS (HR 0.93, P = 0.05) and relapse free survival (HR 0.87, P = 0.003), decreased rates of resistance (OR 0.71, P = 0.01) and relapse (OR 0.75, P = 0.002), but oddly had no effect on CR rate, suggesting that complete response status was disconnected from longer term outcomes (this is actually very common). Subgroup analysis identified cytogenetic status as an important variable for response to GO. On the downside, the risks of grade 3–4 nausea/vomiting, diarrhea and liver aspartate transaminase (AST) elevation were increased in the GO arm.

Additional analysis is due this spring, and will likely be available at AACR or ASCO.

GO provided clear clinical POC that targeting CD33 could be an effective strategy for AML, and Seattle Genetics (SGEN) had also developed a naked antibody called SGN-33 (lintuzumab) that failed in phase 2b, demonstrating no efficacy benefit compared to chemo alone. Seattle Genetics has therefore developed a second-generation anti-CD33 targeting mAb, as an ADC. The mAb is coupled to pyrrolobenzodiazepine (BPD) a DNA minor groove-binding molecule that effectively stops tumor cell division and induces cell death. The resulting ADC is called SGN-CD33A. A phase 1 trial in AML just got underway (NCT01902329).

A very different mechanism for targeting CD33 is being developed by Amgen (AMGN) using technology acquired when they bought Micromet. Micromet developed a bi-specific antibody technology termed BiTE. BiTE antibodies fuse two single-chain mAbs, one that binds CD3 on T cells and a second that binds tumor cell antigens. The idea is to redirect T cells to selectively lyse tumor cells. AMG330 is a BiTE antibody with CD33 antigen recognition. This therapeutic is still in preclinical development.

A different bispecific modality is BiKE, in which an NK cell targeting mAb (anti-CD16) is coupled to anti-CD33. The idea is to trigger NK cells to degranulate thereby killing the tumor cells. Nice idea, probably a long shot, in preclinical development.

Yet another approach to targeting CD33 has been developed in the context of CAR-T technology. CAR-T technology is based on introducing a tumor-targeting construct to the patients own T cells ex vivo. A lentiviral vector expressing a chimeric antigen receptor with specificity for AML antigen CD33 is coupled with CD137 (4-1BB) and CD3-zeta signaling domains. A low dose of modified T cells are then re-infused into the patient. This technology is dubbed CART-33. The cells rapid proliferate and are activated in the presence of antigen (ie. the tumor cells), inducing a robust and long-lived anti-tumor response. A phase 1/2 trial has begun in Beijing (NCT01864902). We can expect additional trials to be added. This therapeutic approach has worked well in advanced lymphomas (with CD19 as the antigen). The technology, licensed by Novartis, is one to watch very closely.

Finally, radioactively labeled anti-CD33 mAbs have been developed, including conjugates of anti-CD33 mAb M195 to 131-I and 213-Bi. The latter conjugate was run in a Phase 1 trial but the clinical trial literature here is sparse. Other radiolabeled mAbs used for AML treatment include a 131-I-conjugated anti-CD33 mAb BC8 and a Y90-conjugated anti-CD45 mAb. Both are undergoing clinical testing at the Fred Hutchinson Cancer Center, apparently with very promising results. In general, radiolabeled mAbs that emit β-particles, such as I131-anti-CD33, Y90-anti-CD33, and I131-anti-CD45, deliver high doses of radiation to the bone marrow and are used as pre-conditioning prior to SCT. Re188-anti-CD66c also falls in this catagory. Short-ranged α-particle emitters like Bi213 Bi-anti-CD33, are used to treat low-volume or residual disease.

Another company that is using bispecific technology to target AML to activated T cells is Macrogenics (MGNX). They have developed an anti-CD3/anti-CD123 DART mAb MGD006, partnered with Servier. This Dual Affinity Re-Targeting (DART) construct is built from 2 different polypeptides, each comprising the VH of one antibody in tandem with the VL of the other antibody, creating a heterodimer that is stabilized by disulfide binding. This construct binds to both CD123 and to CD3 in the human T-cell receptor complex. A phase 1 trial should begin this year.

CD123 is the IL-3 receptor, expressed on myeloid lineage cells and elsewhere, highly expressed on AML cells. It also is expressed on leukemic stem cells, leading to the hypothesis that targeting CD123 might prevent relapses by eliminating residual tumor progenitor cells from the bone marrow niche. Recent data suggest that mutations in the signaling chain of CD123 may contribute to oncogenesis in some lymphomas and leukemias, including AML. Early POC was provided by the mAb 7G3, which showed potent in vitro and in vivo killing of human AML cells. This mAb did not undergo further development, although it appears occasionally in the radio-immunotherapy literature, e.g. as In-111-NLS-7G3 where NLS is a 13-peptide linker.

An anti-CD123 mAb already in Phase 1 is CSL362, a novel monoclonal antibody therapy. This antibody has been engineered antibody to efficiently recruit NK via the Fc portion of the antibody, so this is a classic antibody-mediated cytotoxicity approach. The mAb is being developed by CSL LLC and is partnered with Janssen.

 Stemline Therapeutics (STML) is developing SL-401, which is comprised of the IL-3 protein conjugated to a truncated diphtheria toxin, a potent inhibitor of protein synthesis. This construct reportedly has anti-tumor potency against tumor cell lines and primary tumor cells in the femtomolar (10-15 M) range. SL-401 is in Phase 2a in AML. That trial should report out preliminary data this year.

Of great interest is the CAR-T technology as applied to CD123 (CART-123). The technology is the same as discussed above for CART-33, and is in preclinical development. Again this is technology developed at U Penn and licensed to Novartis. We won’t get into the competitive landscape of modified T cell technologies, nor the intellectual property wars, a subject perhaps for another time.

A few other biologics to keep an eye on:

– Trebananib (AMG386) is a peptibody targeting the Angiopoietin 1/2 proteins. These are ligands for Tie2, a receptor on endothelial cells that promotes tumor angiogenesis. Peptibodies are petides fused to the Fc domain of an antibody. The peptide provides the parget recognition. A phase 1 reported at ASH that the therapeutic was safe and showed preliminary signs of efficacy in adult AML (Abstract #2710).

– Igenica is a private company that just received Series D funding of 14MM USD to advance IGN523 into the clinic. The funding round was led by Third Rock Ventures. IGN523 is an anti-CD98 antibody that targets both the tumor cells and tumor stem cells. CD98 is the neutral amina acid transported expressed on dividing lymphocytes, and it has been argued that IGN523 functions not only by inducing antibody-mediated cytotoxicity (by NK cells and CD8+ T cells) but also by blocking activity of the receptor.

– CXCR4 has emerged as an attractive target in AML, beyond the standard application of CXCR4 to mobilize stems cells. More recent work has focused on using CXCR4 antagonists like plerixafor (a small molecule) for chemo-sensitization (see ASH 2013 abstract #2680). More direct targeting is being pursued by Bristol Myers Squibb (BMS), with the antibody BMS-936564 (ASH abstract #3882), currently in phase 1 for AML (NCT01120457). Other CXCR4 agents are in development.

– other antigens have been recently identified.

If we look broadly at the biologics being developed for AML a few things jump out. First, there are no home runs, as we have seen in other lymhomas such as Non-Hodgkin’s lymphoma, where the anti-CD20 mAb rituximab showed dramatic response rates early in clinical development. Second, it’s still early for nearly all of these agents, with the exception of the GO ADC. Third, and this is a very common theme, combination therapies will be required to control this brutal disease. We saw in the review of small molecule therapeutics that companies and the NCI are co-sponsoring trials in order to move clinical practice forward, and we should expect similar collaboration as the biologics move ahead (indeed we already see this with the GO combo trial).

Tomorrow we’ll talk about the role of immune-checkpoint therapeutics in AML, a field with great promise.

ANTICIPATING NEW THERAPEUTICS AND FORECASTING TREATMENT TRENDS FOR ACUTE MYELOID LEUKEMIA – PART 1

AbbVie, AML, Companies - stock symbols, drug mechanism of action, Flt3, HDAC, Jak2, Karyopharm, Merck, midostaurin, Novartis, Onyx Pharma, panobinostat, Pathways for Drug Development, plerixafor, Quizartinib, sorafenib, vorinostat

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 by Paul D Rennert, February 11, 2014

In looking at Acute Myeloid Leukemia (AML) we see a cancer field right on the cusp of change in clinical practice. Standard of care chemotherapy regimens and stem cell transplantation protocols have proven to be of limited utility, especially in older patients. However, potentially big advances in care are being made, with exciting news coming out regularly. As we move toward the spring Medical Conference season, we felt an overview of this rapidly evolving area of oncology would be timely.

AML is a rapidly growing cancer of myeloid lineage cells that proliferate in the bone marrow and interfere with normal hematopoiesis. AML typically arises in the context of defined genetic mutations. For example, translocations of chromosome 16 disrupt RUNX1 gene activity and are one of the several underlying causes of Core Binding Factor AML. CBF-AML). Since RUNX1 regulates the transcription of many genes, the effect of its disruption is complex. CBF-AML patients are generally responsive to chemotherapy initially, although up to half of these patients will relapse over time due to additional genetic mutations.

Mutation of the FLT3 protein is the most common genetic abnormality in AML, found in about 30% of patients. This is a genetic characteristic associated with poor prognosis. The most common FLT3 mutation, FLT3-ILD, is caused by an tandem duplication within the coding region of the gene. The resulting protein drives hyper-signaling and oncogenic cell responses. Mutations that change the active site of the protein, causing unregulated phosphorylation, have also been described. Mutations in the receptor tyrosine kinase c-Kit are also associated with oncogenic signaling in AML. Both of these pathways cause mutiple downstream effector pathways to be activated. The JAK2 mutations, commonly see in myelofibrosis and other myeloproliferative disorders, are rare in AML but when characterized can potentially be treated with Jak2 inhibitors.

According to a recent market research analysis                           (http://www.transparencymarketresearch.com/acute-myeloid-leukemia-therapeutics-market.html) a total of 62,226 new cases of Acute Myeloid Leukemia (AML) were recorded in 2010, with 95,000 predicted new cases for 2015 and nearly 130,000 predicted new cases in 2020. Note that as of February 2014 approved agents for AML remain limited to chemotherapeutics (http://www.cancer.gov/cancertopics/druginfo/leukemia#dal2). Despite the lack of new targeted drugs, the AML therapeutics market was nearly 240 MM USD in 2011. At the current rate of growth the AML market could reach over 700 MM USD by 2018. These numbers are based on the analysis of future AML drugs growing at a 17% compound annual growth rate from through 2018.

Numbers like these are continuing to drive intensive research into effective, novel therapies for AML. It only helps that in many cases such therapeutics find use in other hematopoietic diseases such as Chronic Myeloid Leukemia (CML) and in the B cell lymphomas, including Hodgkin’s Lymphoma and the non-Hodgkin’s Lymphomas (NHL).

 There is obvious unmet medical need for effective therapies in AML since this is a disease characterized by quick relapse after therapy with grim survival statistics. In some older patients, survival is as little as 1-1.5 years despite first and second line treatment regimens.

What’s exciting from the drug development and biotech investment perspectives is that the AML treatment landscape is advancing simultaneously across therapeutic modalities. This rapidly changing landscape give us a chance to look at targeted small molecule drugs, monoclonal antibodies (naked, bi-specific, radiolabelled, immunotherapeutic, ADC), targeted T cells and other novel technologies.

 We can then ask ourselves: who will the winners be in 5 years?

 A) Targeted small molecule drugs.

Lets just be clear upfront that the goal of these targeted therapies is to get patients who have relapsed, or are refractory to chemotherapy, to a complete response (CR) with minimal residual disease (MRD) so they can qualify for an allogeneic stem cell transplant (SCT). That’s a lot of acronyms but what this is really saying is that for most patients the goal is a modest one – we are not asking for a durable remission, at least not yet.

 A variety of established drugs are being tested in AML. Also, the identification of oncogenic mutations in FLT3 and cKIT has driven interest in developing new tyrosine kinases inhibitors (TKIs) for AML.

 Sorafenib (NexavarTM; Bayer and Onyx) is a dual targeting drug that blocks RAF signaling (and therefore the MEK>ERK signaling) and also the growth factor receptor tyrosine kinases VEGFR and PDGFR. The NCI is running a large phase 3 trial enrolling new onset pediatric AML patients (NCT01371981) with sorafenib being given in combination with various chemo regimens.  Bayer and Onyx are running several earlier phase AML trials. An interesting phase 1 trial in patients 18 or older combines sorafenib with plerixafor and G-CSF (NCT00943943). The idea here is to have the CXCR4 blocker (plerixafor) and the growth factor (G-CSF) flush tumor cells, and also tumor stem cells, from the bone marrow and lymph nodes so that they are more sensitive to sorafenib treatment. This trial is co-sponsored by Genzyme/Sanofi, which owns plerixafor.

Another interesting trial is the Phase 1/2 study of the combination of sorafenib, with vorinostat, and bortezomib (NCT01534260). Here we have a proteasome inhibitor and an HDAC inhibitor added to growth factor and signaling inhibition provided by sorafenib. This potent combination is being used in patients with a poor genetic risk profile, including FLT3-ILD positive tumors. This study is co-sponsored by Bayer/Onyx, Millennium/Takeda and Merck Sharp & Dohme Corp.

Bristol Myers Squibb is running an interesting trial (NCT01620216) in which AML and acute lymphocytic leukemia (ALL) patient samples are analyzed for sensitivity to drug treatment ex vivo, after a period on drug in the trial, as follows:

“An in vitro kinase inhibitor assay will be used to determine the sensitivity of primary leukemic cells to four kinase inhibitors/drugs:

Drug: Sunitinib, 50 milligrams (mg) qd, with or without food, for 4 weeks

Drug: Dasatinib, 100 mg qd…possible escalation to 140 mg qd for 28 days

Drug: Nilotinib, 400 mg twice daily for 28 days

Drug: Sorafenib, 400 mg (2 tablets) orally twice daily without food for 28 days

Drug: Ponatinib, 45 mg dose once per day

Sunitinib (Sutenttm; Pfizer) makes sense as a pan-growth factor receptor inhibitor; dasatinib (Spryceltm; Bristol Myers Squibb) is a Src and c-Kit inhibitor and is a reasonable choice for AML; nilotinib (Tasignatm; Novartis) is a pretty specific Bcr-Abl kinase inhibitor and is probably only being used for the ALL population – and even there only 25% of ALL patients carry this translocation; sorafenib we discussed earlier; ponatinib (Iclusigtm; Ariad) has a grab bag reactivity profile, hitting the BCL-ABL kinase, FLT3, RET, c-KIT and the FGFR, PDGFR and VEGFR growth factor receptor kinases. This is a dangerous drug, with a very narrow FDA approval in CML, and I suspect enrollment in this little exploratory trial will be stopped if possible.

If I had to guess I would say that this rather odd trial design has several goals. One is to look for signs of efficacy, although a month is pretty short duration. One might also look for patterns of resistance to therapy, which would be very interesting. Since this is BMY, I’d be surprised if they weren’t also looking at cell surface markers for possible immunotherapy treatment – more on this subject later.

Results from a dasatinib trial in CBF-AML were recently presented at the American Society of Hematology (ASH) conference (Abstract #357). Dasatinib was added to induction and consolidation chemotherapy in newly diagnosed AML patients. Unlike the rrAML population, the CBF-AML population can experience sustained periods of remission prior to relapsing, especially in younger patients. Since some of the relapses are driven by gain of function mutations in c-Kit, dasatinib should prevent at least those clones from becoming established. Early results looked good but longer term data are needed to see if this regimen will remain effective.

Imatinib (Gleevectm; Novartis) another Bcr-Abl, c-Kit and PDGF-R inhibitor, has been tested in multiple AML trials, but the results have not led to approval for use in AML. An interesting trial of the cytotoxic/immunomodulatory agent lenolidomide (Revlimidtm; Celgene) plus chemotherapy is being run by the NCI (NCT01246622). Lenolidomide has been approved for the treatment of a different bone marrow resident cancer, multiple myeloma (MM).

Anyway there is a lot of similar clinical trial work being done – using approved drugs in this new indication and looking for efficacy. This is ultimately good both for patients and the drug development companies.

Lets move on to some newer drugs in the pipeline. The FLT3 inhibitors give us a sense of the difficulty here, with low response rates as monotherapies.

Quizartinib (Ambit Biosciences; AMBI) remains stuck between phase 2 and 3 for relapsed/refractory (rr) AML. This drug is a FLT3 inhibitor with a somewhat tortured history, having been partnered for a time with Astellas, then returned, then running nicely in the clinic before running into disagreement with the FDA over approvable endpoints and safe dosage. In early December the company announced it would have to run a phase 3, likely with lower starting doses, in order to obtain FDA approval. Investors were hoping the company could file on its phase 2 trials. Notably, later in December Ambit showcased its’ quizartinib data from the FLT3-ILD rrAML trial, in which a 50% response rate (50% or greater reduction in leukemic blast cells) was reported with relatively low doses of drug. Unfortunately, it will be a while yet before more news becomes available about this drug.

In the meantime heavy hitter Novartis is already in phase 3 with its’ FLT3 and Protein Kinase C inhibitor midostaurin. The phase 3 in newly diagnosed patients is being run by the NCI (our tax dollars at work), along with The Alliance for Clinical Trials in Oncology and the Cancer and Leukemia Group (NCT00651261). A trial of midostaurin administered with or without bortezomib in adult rrAML patients is being run by Novartis and Millennium/Takeda (NCT01174888). Preliminary results were presented at ASH (abstract #3966). While response rates were impressive the toxicity was extreme, and this seemed to be due to the bortezomib dose, which was adjusted. Phase 2 trials in adult patients who carry c-KIt, FLT3-ILD, and various other mutation or cytogenetic markers are also underway (NCT01830361, NCT01846624). A phase 2b midostaurin  monotherapy study published several years ago showed modest improvement in AML patients with mutated FLT3; this study recognized the need for combination therapy to improve the clinical response (http://www.ncbi.nlm.nih.gov/pubmed/20733134).

Another FLT3 inhibitor, lestaurtinib, is the subject of 2 NCI sponsored trials in pediatric ALL/AML but drug development of this agent seems to have stalled when Teva bought Cephalon. Another FLT3 inhibitor is PLX3397 (Plexxikon) which has activity against  KIT, CSF1R and FLT3. This drug is in a phase 1/2 trial in adult rrAML (NCT01349049).

One of the major challenges for FLT3 inhibitors is breadth of action. These inhibitors work best on patients who have mutated FLT3 and are less effective in patients with normal FLT3. Also, secondary mutations have already been discovered in response to FLT3 inhibition. Specifically, in those patients who have mutations in the active site of the kinase, so-called gatekeeper mutations arise, conferring resistance to the drug.

A dominant theme in recent drug development for AML has been built on the observation that proteasome inhibitors can impact cancers of the bone marrow. Disruption of proteasome activity blocks a wide spectrum of cellular activities, and is particularly effective against rapidly dividing cells (like leukemic blasts) but also relatively quiescent tumor stem cells, that require specific proteasome-dependent signaling pathways (e.g. NK-kB). Bortezomib (Velcadetm, Millennium/Takeda) has shown activity in older patients when combined with chemotherapy. A phase 3 combination trial with sorafenib in newly diagnosed AML patients is underway, sponsored by the NCI (NCT01371981).

Carfilzomib (Onyx Pharmaceuticals) is in an early stage trial for AML, along with extensive trials in MM, B cell lymphomas, etc. The drug is furthest along in MM, now in phase 3 (NCT01568866). Early reports so far have suggested that this drug has an activity profile similar to bortezomib, but may have a better safety profile. This is an interesting drug (and company) to watch. They have a second generation oral version of carfilizomib, oprozomib, in phase 1 MM trials. Millennium/Takeda are developing ixazomib in MM and lymphomas. An AML trial is listed but not yet recruiting.

A third theme that we can follow in AML therapeutic drug development is the use of drugs that impact epigenetic gene regulation. Because AML is driven by genetic translocations, gene regulation at the level of chromatin structure is disrupted. There are two processes at work here that can be targeted. One is the aberrant methylation of CpG islands in gene promoter regions, which can be targeted by DNA methyltransferase inhibitors. The second is changes in the conformation of chromatin caused by dysregulated histone acetylation. This process can be therapeutically targeted using histone deacetylase [HDAC] inhibitors.

The HDAC inhibitor vorinostat (Zolinzatm, Merck) has been extensively studied in AML, and is currently in a phase 3 trial with chemotherapy for young patients with newly diagnosed disease (NCI; NCT01802333). Vorinostat monotherapy was generally ineffective, but combination with chemo agents proved much more potent. As detailed at ASH in December (Abstract #2684), newly diagnosed and rrAML patients were enrolled in a phase 2 expansion study. Of 75 patients, 57 patients achieved CR, and 7 achieved CR with incomplete platelet recovery (CRp), for an overall response rate of 85 percent. Median overall survival was 82 weeks and median event free survival was 47 weeks. For patients with the high-risk Flt-3 ITD mutation the 10/11 achieved CR and 1/11 CRp. The ORR = 100% in these patients. Their median overall survival was 91 weeks and median event free survival was 66 weeks. About 25% of the total patients in CR received SCT.

Other combination trials include the sorafenib trial mentioned above, and a trial in combination with antibody therapy (gemtuzumab ozogamicin) for rrAML (NCI; NCT00895934). This trial reported early results at ASH (Abstract #3936). The response rates ere encouraging and about 20% of patients obtained durable remission. There were significant toxicity issues. This drug is very likely to play a critical role in the evolution of combination therapy for AML. We’ll discuss antibody therapies further in Part 2.

Other important HDAC inhibitors in development for AML is panobinostat (Novartis). What’s interesting about the development campaign with this drug is the pairing in multiple trials with 5-azacitidine, a DNA methytransferase inhibitor. In such settings two modes of epigenetic regulation are being targeted simultaneously. One of these studies published findings last month                                 (http://www.nature.com/bcj/journal/v4/n1/full/bcj201368a.html) and demonstrated good tolerability and reasonable response rates. Clearly, this combination should move forward in the context of chemotherapy or other drugs. Of note the DNA methyltransferase inhibitor decitabine (Dacogentm, MGI Pharma) is already approved for AML. There was also a presentation on the HDAC inhibitor entinostat (Syndax Inc) with 5-azacitidine in myeloid neoplasia (Abstract #2777), and there are several clinical trials listed for AML, however this drug is mainly being used in solid tumor trials.

Other interesting drugs in this area include alisertib, an Aurora A kinase inhibitor (Millennium/Takeda) being tested extensively in B and T cell lymphomas and in solid tumors. There are several AML trials including a phase 2 trial completed by MLMN (NCT00830518). Selinexor, (Karyopharm) a selective inhibitor of nuclear export, in in phase 1 trial for advanced AML. Abbvie’s Bcl2 inhibitor ABT-199 is also in an AML trial.

If we take a step back we can appreciate that in small molecule development Novartis, Merck and Onyx are placing big bets in this therapeutic area. We’ll sort out the best looking therapeutics as we dig in a little deeper.

In Part 2 we’ll take a look at the biologics landscape, and begin to draw the bigger picture.

The Cancer Genomic Ecosystem

AML, cancer, CLL, genomics, melanoma, mutations, resistance, signaling

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There have been several important recent advances in our understanding of tumor genomic ecosystems, and these advances have interesting implications for drug discovery in oncology.

The Journal Nature recently published a large data set on gene mutations in 21 distinct tumor types (http://www.nature.com/nature/journal/v505/n7484/full/nature12912.html). Much of the data came from the The Cancer Genome Atlas (TCGA) database, with additional data generated by the study authors. This study is sufficiently powered to uncover significance in several different ways. There is a cluster of mutations that are significant only in the combined tumor analyses, that is, when lumping different tumor types together. Conversely there a large cluster of mutations that are significant only in the analysis of individual tumor types, that is, the significance is lost if you look too broadly. Therefore these are genes that are important for specific tumor types. Finally there is a large cluster of gene mutations that are significant in both the combined analyses and in individual tumor analyses. This complexity of analysis is nicely shown in Figure 3 (http://www.nature.com/nature/journal/v505/n7484/full/nature12912.html#f3).

I spent a fair amount of time staring at this figure and going through the supplemental data (posted online and see also http://www.tumorportal.org/) and there are some results that I found interesting. First, the study confirmed many known cancer-related genes. The study also identified a fair number of new cancer-related genes mutated across or within tumor types, although these were found at the lower levels of significance. This is because they are mutated at a low rate, or the sample size for a particular tumor type was small, or both. The authors are transparent about this, and call for larger studies to increase sample size. This does beg the question as to the rate of gene mutation below which the knowledge is no longer actionable (because there will be so few patients), regardless the data will be critical to understanding tumor pathway biologies. Another interesting question is the extent to which new patterns of gene-mutation will emerge across tumor types, allowing binning (across tumor types) to complement subsetting (within a tumor type). Finally, the data might allow a different type of query, which is to ask which combinations of mutations are found within specific tumor types.

I want mention a few of the more common mutations, because these data held some surprises for me (although some readers know all this already, I’m sure). First, the best known cancer-related gene mutations cluster at the very highest levels of significance both across the 21 tumor types and within specific tumors. This makes sense, as these genes include those that contribute obligate cancer mutations: TP53; PTEN, PIK3CA and PIK3R1; KRAS, BRAF and NRAS; APC; EGFR, etc. There were a few genes in this category that surprised me, not so much because they made the list but because these at first glance appear more common than I had thought. GATA3 is a good example. Mutations in this gene are most commonly see in breast cancer but there are enough mutations in other tumor types to drive significance in the pooled tumor analysis, even though no tumor type other than breast is significantly associated with GATA3 mutations. Examination of the FTL3 data reveal a very similar pattern: mutations are significantly associated with acute myeloid leukemia (AML), as is well known, but also present in other tumor types, notably endometrial tumors and lung adenocarcinomas. When the mutational data across tumor type is pooled, significance is achieved. What are we do with such data? I think the answer perhaps is to simply know that these mutations can occur, and to look for them when typical mutations are missing in a given patient’s tumor. Such cataloging is of course the goal of personalized medicine. The other use of such data is to raise awareness of rare drug resistance mutations that may arise when targeting the major tumor oncogenic pathway in a particular tumor type. Many examples of this phenomena have been described (more on this below).

A different pattern emerges when we look at some other genes that are commonly mutated across tumor types but whose significant in these analyses is lower, due to a lower mutational rate. IDH1 is a good example here, having significant association with AML and glioblastoma multiforma, as is well known, but also with multiple myeloma (MM) and perhaps chronic lymphocytic leukemia (CLL). IDH2 is also most commonly associated with AML, but is present in colorectal cancer at “near significance” (love that fuzzy language). Notably, no other tumor metabolism genes appear in the analysis.

There are same gaps too I think. Looking at those genes that are significantly mutated only in a specific tumor type or types, we find some interesting genes. TGFBR2 has been described as a mutational driver in colorectal cancer, along with SMAD4. In the present analysis SMAD4 and SMAD2 are found to be significantly mutated in colorectal cancer, but the TGFBR2 mutation rate only reaches significance in Head and Neck cancer, although a few mutations do appear in the colorectal cancer data set used. Either the original studies are incorrect, which does not make sense biologically (TGFBR2 protein signals through the SMAD pathway), or this is an example of sampling error. Again, bigger data sets may be needed. Other tumor-type restricted patterns of gene mutation are very well known, such as EZH2 and CARD11 mutations in diffuse large B cell lymphoma (DLBCL). The CARD11 observation is interesting, as these mutations are associated with activation of MYD88, a gene known to be mutated in DLBCL and CLL.

There are lots of examples like these, and the data are easy to see and analyze: this is fun data to play with so have at it (see http://www.tumorportal.org/).

There is much discussion in the paper on new genes identified, and we’ll have to see how much of it is actionable at the drug development level.

That brings us to a different data set. If you go to the tumor portal you can sort by tumor type. Choosing melanoma, a highly mutated cancer, brings forth a whole spectrum of genes. Here’s a screengrab right from the tumor portal site (http://cancergenome.broadinstitute.org/index.php?ttype=MEL)

Screen Shot 2014-02-02 at 11.51.43 AM
In the table above, blue refers to known cancer-related genes, red indicates genes whose function is relevant to cancer biology, and black are novel genes. As many readers know, BRAF mutations are the canonical melanoma oncogenic driver, signaling through the MEK/ERK pathway to drive melanoma cell proliferation, migration and metastasis. Antagonists of the BRAF and MEK proteins have emerged as the best line of defense against melanoma, but its a complicated fight. BRAF inhibitors were developed several years ago, starting with vemurafenib (Roche). Although BRAF inhibition induced responses in many melanoma patients, BRAF resistance mutants and MEK1 escape mutations evolve quickly and patients relapse. Common BRAF resistance mutations include V600E and V600K mutations that confer protection against the first generation drugs. Second generation inhibitors that target the resistance mutations were developed, such as dabrafenib (GSK). In addition, the MEK inhibitor trametinib (GSK, Japan Tobacco) was approved last year for use in treating melanoma. Several weeks ago the combination of these two drugs was granted accelerated approval for the treatment of advanced (metastatic) or unresectable melanoma that is positive for either mutation (V600E or K). This is a great example of cancer genetics=driven drug development in action.

However, other mechanisms of resistance are independent of BRAF mutational status because of additional MEK resistance mutations. These additional mutational strategies were discussed in a series of papers published online on November 21, 2013, in Cancer Discovery. These studies used tumor samples from patients that had relapsed after either BRAF inhibitor of dual BRAF/MEK inhibitor therapy. Mutations were found in the MEK1, MEK2, ERK1, ERK2 pathway and the PI3K, AKT1, PTEN pathway (PTEN is a negative regulator of PI3K signaling to mTOR and AKT1). The papers were reviewed in the January 9th issue of SciBx.

What does this single example tell us about the mutational landscape and drug discovery. First let’s note that some of the resistance mechanisms for melanoma do not show up in the proposed melanoma mutational landscape chart above, that is, these did not appear in the tumor ecosystem until that ecosystem came under selective pressure via drug treatment. This has 2 implications: the first is that the TCGA type overview of tumor mutations is just one source of data and following patients longitudinally as they experience therapy is another source of data. The other implication is that the mutational landscape contains putative additional mechanisms of escape at least in some patients. So using our melanoma example, we see in the table evidence of other potential escape pathways (NRAS, several checkpoint genes, and KIT stand out to me). So how many drugs will any individual patient need to keep a rapidly evolving melanoma under control?

The good news is that drug developers have taken notice and ERK1/2. AKT and PI3K inhibitors of various specificity are under development. The bad news I guess is that this is just one example of how complicated cancer therapy is likely to become. One good question not addressed here is how the immune checkpoint drugs will overlay with targeted therapies, for melanoma and many other tumors. Thats a question for another day.

stay tuned.

ASH13 just around the corner – quick update of CAR-T technology

ALL, AML, ASH13, chimeric antigen receptors, CLL, immunotherapy, myeloma

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December 2, 2013.
by Paul D Rennert 

Part 7. Chimeric Antigen Receptor T cell technology (CAR-T) in the treatment of hematopoietic malignancies.

The American Society of Hematology Meeting will take place in New Orleans, December 7 – 10, 2013. The abstracts are available at http://www.hematology.org/Meetings/Annual-Meeting/Abstracts/5810.aspx
Having detoured briefly into myelofibrosis (see parts 6a and b), there are just a few more subjects to try to cover this week. With luck and time, I’ll get through this bit today and then maybe on to lymphoma genetics, we’ll see.
This is from the introduction to Carl June’s seminal 2011 NEJM case report:
“We designed a lentiviral vector expressing a chimeric antigen receptor with specificity for the B-cell antigen CD19, coupled with CD137 … (4-1BB) and CD3-zeta … signaling domains. A low dose (approximately 1.5×10^5 cells per kilogram of body weight) of autologous chimeric antigen receptor–modified T cells reinfused into a patient with refractory … CLL expanded to a level that was more than 1000 times as high as the initial engraftment level in vivo, with delayed development of the tumor lysis syndrome and with complete remission. Apart from the tumor lysis syndrome, the only other grade 3/4 toxic effect related to chimeric antigen receptor T cells was lymphopenia.” (Porter et al. 2011. NEJM 365: 725-733). The therapy induced long term remission is a patient who had failed 4 rounds of rituximab+chemo, and then had failed alemtuzumab, anti-CD52, therapy. Pretty amazing.
The anti-CD19 CAR is essentially an antibody fragment containing a single chain Fv (antigen binding domain). The CD3-zeta chain induces T cell activation and the addition of the 4-1BB cytoplasmic domain ensures prolonged and robust response – 4-1BB is in immune checkpoint activator, and is gaining some favor in its own right in immunotherapy, through the development of agonist anti-4-1BB antibodies. The CAR-T components are introduced to the patient’s own T cells ex vivo via lentivirus transduction, then given back to the patient in hopes of inducing a T cell mediated immune response to the cancer (e.g. a CD19+ CLL). The original case reports were followed for up to 3 years, as reported in Abstract #4162. Of 14 patients treated in the pilot studies, the ORR = 57% (21% CR and 30% PR). 43% of patients did not respond. Of the PR cohort, 40% progressed within 4 months. So that’s about 1/3 of patients with a durable response.
Additional clinical trials have been funded via collaboration with Novartis, who has bought the technology and patents. A few of these are updated at ASH. The CLL and ALL data for patients treated with the anti-CD19 CAR T cells (CTL019) are summarized in Abstract #163. 24 rrCLL patients have been treated using 2 different protocols that vary by the number of CTL019 cells given back to the patient. The response rates were CR = 21%, PR = 29% (so ORR = 50%) and non-responders = 50%. In pediatric ALL (n=14) the CR = 57%; the rest of the patients (43%) either did not respond or progressed. In adult ALL, all 3 patients had a CR (=100%). CRs were always accompanied by in vivo expansion and persistence of CTL019 cells. Tumor cells were eliminated from circulation and also, importantly, from bone marrow. Molecular analyses showed that tumor cells were essentially eliminated in patients with CR – this is defined as minimal residual disease (i.e. not detectable). Additional data specific to these studies are reported in Abstract #873 (CLL) and Abstract #67 (ALL) – the latter study reports persistence up to 15 months. Another group at U Penn reported similarly high RRs in ALL. Lee et al (Abstract #68) report the use of an CD19-CD28-CD3zeta CAR construct to engineer t cells for use in ALL, with an initial CR (n=7) of 71.5%, with other 2 PR responders and 2 non-responders. These are impressive early data from multiple studies.
Steve Rosenberg’s group is also reporting use of anti-CD19 CAR-T cells, these made using a gamma-retrovirus construct to genetically modify the T cells. The technology differs also by use of the CD28 signaling domain instead of 4-1BB, along with CD3-zeta. Of 14 patients with rrCLL, rrDLBCL or primary mediastinal BCL, 36% achieved a CR and 43% a PR, the rest being non-responders or SD. All responders (PR + CR = 79%) were ongoing at the time of abstract submission. The study will be further updated at the meeting. The trial was funded under a CRADA-based collaboration between the NCI and Kite Pharma, a private biotech company.
Given the compelling response rates observed, it is unclear whether the ex vivo selection and expansion methods employed by the MD Anderson group will add benefit. Laurence Cooper and colleagues will present a CD19 CAR technique that utilizes artificial antigen-presenting cells to select the T cell population that is then given following hematopoietic stem cell transplantation in ALL and NHL patients (Abstracts #166 and #4208). Their very early results will be updated at the meeting. Additional efforts targeting CD19 include the trial in rrCLL patients who have received only 1 prior chemotherapy regimen; the idea is that these patients are earlier in the disease course and may have better response rates. It is not possible to tell from the Abstract (#874) if this effort is succeeding, but an update is promised at the meeting.
Turning from the CD19-directed technologies, Carl June’s group is presenting the first clinical data on the use of engineered T cells in multiple myeloma. The T cells are expanded using CD3/CD28 beads (a technology I worked on 20 years ago at Repligen, in the context of HIV therapy) and are engineered to express a modified TCR that recognizes the MM antigens NY-ESO-1/LAGE1. The recognition of this peptide complex is HLA-class restricted, so the patients are screened in advance for responsive HLA haplotypes. The T cells are infused followed depletion and stem cell transplantation, so CAR-T is used here in the context of adjunct therapy. Best response ORR = 100%, although some patients have since progressed. An update will be given at the meeting. Also of note is a trial in which this novel CAR-T therapy is used in a non-transplant setting (no data available yet). An interesting twist is the use of kappa-light chain of surface immunoglobulin expressed on malignant B cells (as opposed to lambda light chain expressed by most normal B cells? – I guess that’s right). A group from Baylor, funded by Celgene, will present Phase 1 data (Abstract #506). Another CAR antigen technology in preclinical development at U Penn targets CD123 for AML (Abstract #143). Preclinical data from the OSU group show that a different MM antigen can be used in the CAR-T setting. Abstract #14 shows that a CS-1 directed CAR works in a mouse xenograft model. I like the straightforward description of the technology: “We successfully generated a specific CS1-CAR construct with a lentiviral vector backbone, sequentially containing a signal peptide (SP), a heavy chain variable region (VH), a linker, a light chain variable region (VL), a hinge, CD28 and CD3epsilon.” Simple, right? Finally, Haso et al from the NIH compare CD22-targeting CAR constructs using different signaling chains (4-1BB v CD28) in preclinical mouse models of ALL, and report superior results using the 4-1BB construct (Abstract #1431). This is nice as they used a humanized mouse model, the NOD/SCID/Common gamma chain KO mouse (NSG), engrafted with a human ALL line. Love the humanized mouse technology, right up my alley.

A persistent theme in the evolving treatment of leukemias and lymphomas is the use of combination therapies. We see a similar trend developing with CAR-T technologies. Paolo Ghia et al combine a CAR directed to CD23 along with low dose lenalidomide treatment using the Rag2/Common gamma chain KO humanized mouse model and cell from CLL patients – nice work (Abstract #4171). A second study evaluated the use of mTOR modulation in the context of CAR-T therapy (Abstract #4488). As this technology continues to advance we can expect to see additional uses of targeted or other therapies in combination.