Shares of SuperGen, Inc. (SUPG), which climbed as high as $2.89 on expectations for positive trial results, reached a new 52-week low of $1.71 in July 2010 following the negative top-line news.  SuperGen receives a 20-30% royalty on worldwide sales of Dacogen from its development and commercialization partners – Eisai in North America and Johnson & Johnson (JNJ) outside of North America.

Despite the negative top-line results, shares of SuperGen have since rebounded and reached a new 52-week high in April 2011.  Optimism may stem from the fact that both Eisai and Johnson & Johnson are continuing to analyze the data and planning to move forward with North America and European regulatory filings in 2011 based on the primary analysis and secondary endpoints.  Accordingly, investors will anxiously await the detailed Phase 3 results being presented on Monday, June 6, 2011 at ASCO to better gauge the likelihood of FDA approval in AML [Abstract #6504 “Results from a randomized phase III trial of decitabine versus supportive care or low-dose cytarabine for the treatment of older patients with newly diagnosed AML”].

Results from the Dacogen study may also be of interest to investors in Cyclacel Pharmaceuticals, Inc. (CYCC), which recently launched a multicenter, randomized, pivotal Phase 3 trial for the company’s sapacitabine oral capsules as a front-line treatment of elderly patients aged 70 years or older with newly diagnosed AML who are not candidates for intensive induction chemotherapy.  Unique among drugs available to treat AML patients, sapacitabine is the only oral agent in late-stage clinical development.  It is also the only candidate to progress into a pivotal study on the basis of survival data from a randomized Phase 2 study.  Historically, sponsors advanced molecules to pivotal development in AML based on Phase 2 studies with primary endpoints of complete remission [CR].

The pivotal Phase 3 study is being conducted under a Special Protocol Assessment [SPA] agreement that Cyclacel reached with the FDA.  The primary efficacy endpoint for the study is an improvement in overall survival from either of the two pairwise comparisons [Arm A versus Arm C, or Arm B versus Arm C] in the following three arms consisting of approximately 150 patients per arm:

• Arm A: sapacitabine administered in alternating cycles with Dacogen
• Arm B: sapacitabine administered alone
• Arm C: Dacogen administered alone

Cyclacel is testing the treatment regimen of sapacitabine administered in alternating cycles with Dacogen [Arm A] in an on-going pilot study, with data expected at ASCO 2011 [Abstract #6587 “Phase I/II study of sapacitabine and decitabine administered sequentially in elderly patients with newly diagnosed acute myeloid leukemia”].  Thirty-day and sixty-day mortality outcomes from this pilot study may be helpful in determining the odds of success in the Phase 3 pivotal study.  To put this in perspective, thirty-day mortality in AML patients aged 70 years or older ranged from 17% to 21% in a recently published Phase 3 study [Harousseau JL, et al, Blood, 2009:114:1166].  Accordingly, results from the pilot study that demonstrate thirty-day mortality with sapacitabine is equal or less than 21% could be encouraging for Cyclacel.

The Phase 3 study builds on promising 1-year survival observed in elderly patients aged 70 years or older with newly diagnosed AML or AML in first relapse enrolled in a Phase 2 study of single agent sapacitabine.  In a disease setting where patients are typically treated with chemotherapy agents like cytarabine for an average of 1 to 2 cycles, patients in Cyclacel’s Phase 2 study achieved a median of 12 cycles of treatment with sapacitabine.

In addition, approximately 45% of patients in the Phase 2 study had transformed into AML after being diagnosed with myelodysplastic syndromes [MDS] and were previously treated with Dacogen or Celgene Corporation’s (CELG) Vidaza® [azacitidine].  Only newly diagnosed AML patients are expected to be enrolled in the ongoing Phase 3 trial, none of whom had been previously treated with Dacogen or Vidaza and none of whom had relapsed, potentially increasing the odds for a successful trial.

Finally, Sunesis Pharmaceuticals, Inc. (SNSS) will also be presenting at ASCO [Abstract #TPS201, “Adaptive design of VALOR, a phase III trial of vosaroxin or placebo in combination with cytarabine for patients with first relapsed or refractory acute myeloid leukemia”].  Unlike the aforementioned frontline trials being conducted under SPA’s, Sunesis is studying vosaroxin in relapsed/refractory AML in an ongoing Phase 3 trial.  Approximately 450 patients will be randomized to receive either vosaroxin or placebo in combination with cytarabine.

Cytarabine, a generic chemotherapy drug introduced several decades ago, is already a critical part of the treatment for younger patients with AML who are fit to withstand its toxicity.  Unfortunately, several companies that make cytarabine have recently experienced production difficulties and others cannot make the drug fast enough to keep up with demand.  This has resulted in a severe shortage of cytarabine that has reportedly affected leukemia clinical trials being run by the Cancer and Leukemia Group B [CALGB].  Accordingly, investors will be looking to Sunesis for an update on enrollment in the VALOR Phase 3 trial to determine whether or not the cytarabine shortage has been a factor.

Beyond the aforementioned investigational therapies, a researcher in the field of oncology noted that newer, targeted agents will be required to advance the treatment of AML: “My personal opinion on AML affecting the elderly population is that the field is in need of a total revamp whereby certain chemotherapy agents need to be combined with targeted therapies to overcome drug resistance and provide meaningful survival data,” said Daruka Mahadevan, M.D. Ph.D., Director, Phase I Program, Arizona Cancer Center.  “If you can increase the survival of a 70-year old patient by ten years, that would be a real achievement.  Sapacitabine is interesting as it is an oral agent, while vosaroxin in combination of cytarabine may provide short term control – but is unlikely to provide a survival benefit.”

Standard frontline therapy for AML patients under the age of 60 consists of cytarabine  [AraC] combined with an anthracycline [such as daunorubicin or idarubicin] in what is commonly referred to as the 7+3 regimen.  While 45% of elderly patients with AML [70+ years old] achieved a complete response [CR] using this regimen, there was no improvement in overall survival and more than a third of patients died within the first eight weeks of treatment according to a recent study published in the journal Blood[i].  This is consistent with the CR rates of 40%–60% with conventional chemotherapy and disease-free survival of less than 20% at three years referenced in the literature[ii].

Since more than half of AML cases occur in patients over 60 years old, there is a need to develop better frontline therapies in this setting.  With five agents being investigated as frontline therapy for elderly AML patients in late-stage trials, the purpose of this article is to compare and contrast these programs – several of which have near-term catalysts for investors.

Hypomethylating Agents

SuperGen, Inc. (SUPG), Eisai Co. Ltd. (ESALF), and Johnson & Johnson (JNJ)

On June 30, 2010, preliminary results from a Phase III trial of Dacogen® [decitabine] as a frontline treatment for elderly patients [65+ years old] with AML were released.  While Dacogen did not meet the primary endpoint of overall survival, a trend was reported to be evident.  However, the failure to demonstrate an improvement in overall survival was surprising given the favorable Phase II results and the fact that the comparator arm received low dose AraC instead of the aforementioned 7+3 regimen.  Low dose AraC predominantly works in patients with favorable cytogenetics, so it should have been relatively easy for Dacogen to demonstrate a survival benefit.

Shares of SuperGen, which climbed as high as $2.89 on expectations for positive trial results, reached a new 52-week low of $1.71 in July.  Supergen receives a 20-30% royalty on worldwide sales of Dacogen from its development and commercialization partners – Eisai in North America and Johnson & Johnson outside of North America.

While investors appear to be discounting approval of Dacogen as a frontline therapy for elderly AML, there may be reasons for optimism.  For example, both Eisai and Johnson & Johnson are continuing to analyze the data and planning to move forward with North America and European regulatory filings in 2011 based on the primary analysis and secondary endpoints.  In addition, the Phase III study was conducted under a special protocol assessment [SPA] with the U.S. Food and Drug Administration [FDA].

Celgene Corporation (CELG)

In view of Dacogen’s negative Phase III trial results, investors may be skeptical about Vidaza® [azacitidine], another hypomethylating agent currently approved for the treatment of myelodysplastic syndromes [MDS], a pre-cancerous condition that can often progress to AML.  According to ClinicalTrials.gov [Identifier NCT01074047], Celgene is currently enrolling patients in a Phase III, multicenter, randomized, open-label, study of Vidaza versus conventional care regimens for the frontline treatment of elderly patients [65+ years old] with AML.

In December 2008, the European Commission granted marketing authorization for Vidaza as a treatment for patients with higher-risk MDS, chronic myelomonocytic leukemia [CMML], and MDS that transforms into AML with a blast percentage of 20-30% in the peripheral blood or bone marrow.  While Vidaza demonstrated a clinically relevant increase in median survival of 9.4 months [24.4 vs. 15 months] in these settings[iii], it is unclear how the drug will work in AML de novo patients with a higher blast percentage [greater than 50%] that represent half of the elderly patient population.  In view of the fact that Dacogen is more myelosuppressive than Vidaza [see Table 1], and for this reason may be preferred over Vidaza for off-label use in AML, the recent failure of Dacogen only adds to this uncertainty.

Table 1. Percentage of Patients with Myelosuppression from Prescribing Information

Monoclonal Antibodies

Seattle Genetics, Inc. (SGEN)

Seattle Genetics is developing SGN-33 [lintuzumab], an unconjugated IgG1 antibody for the treatment of AML.  Lintuzumab has been shown to induce cell death by both complement and/or antibody-directed cellular cytotoxicity, or as a direct effect of the engagement of the CD33 receptor, which is expressed in most leukemic blast cells but also in normal hematopoietic cells.

In a Phase II study in relapsed/refractory AML patients, single agent lintuzumab demonstrated efficacy in patients with advanced AML; however, the positive effects were confined to patients with low disease burden [blast percentage 5% to 30%].  This suggested that additional development of this agent would be best achieved by combining lintuzumab with chemotherapy.  However, while the addition of lintuzumab to salvage induction chemotherapy was safe, it did not result in a statistically significant improvement in response rate or survival in patients with refractory/relapsed AML in a subsequent Phase III trial[iv].

Seattle Genetics is now conducting a 210 patient Phase IIb study in frontline treatment of elderly patients [60+ years old] with AML with results expected in the August to October 2010 timeframe.  See ClinicalTrials.gov [Identifier NCT00528333] for more information.

While lintuzumab relies on a different mechanism of action, investor’s are understandably skeptical about the success of another anti-CD33 monoclonal antibody in AML.  In June 2010, Pfizer, Inc. (PFE) agreed to withdraw Mylotarg® [gemtuzumab ozogamicin] from the U.S. market, effective October 15.  Mylotarg is an IgG4 monoclonal antibody to CD33 linked to a cytotoxic agent from the class of calicheamicins.  Developed by Wyeth, the drug was fast-tracked to treat patients ages 60 and older with recurrent AML who were not candidates for other chemotherapy.  The FDA approved Mylotarg in May 2000 based upon a surrogate endpoint due to the fact it treated relapsed disease with no other viable therapy.

Four years later, a confirmatory trial was begun to confirm the results of the 142 patients who participated in the three previous clinical trials.  The 2004 trial showed that adding Mylotarg to existing chemotherapy for the treatment of AML provided no benefit and even showed a higher death rate.

Nucleoside Analogs

Genzyme Corporation (GENZ)

In September 2009, the FDA’s Oncologic Drugs Advisory Committee [ODAC] voted 9 to 3 that a randomized, controlled trial is needed to support the proposed label expansion for Clolar® (clofarabine) as a frontline treatment for elderly [60+ years old] patients with AML.  Consistent with the decisions for both Johnson & Johnson’s Zarnestra® [tipifarnib] and Vion Pharmaceuticals’ Onrigin® [laromustine], the committee determined that single-arm clinical study results were not sufficient for approval.

Despite the setback, Genzyme stated in a press release that the company remains committed to the clinical development of clofarabine in this patient population and that the drug is being investigated in clinical trials by most of the leading AML experts and major cooperative leukemia investigation groups in the United States and Europe.

Beyond the frontline setting, Genzyme is also conducting a randomized Phase III trial comparing clofarabine in combination with AraC to AraC alone in relapsed and refractory adult AML patients 55 years old or older [ClinicalTrials.gov Identifier NCT00317642]. Results are expected in 2011.

Note: At the time of writing, Sanofi-Aventis (SNY) has offered to acquire Genzyme for $69 per share.

Cyclacel Pharmaceuticals, Inc. (CYCC)

Cyclacel is developing sapacitabine for the treatment of AML, MDS and non-small cell lung cancer [NSCLC].  Sapacitabine is unique among the frontline, elderly AML landscape as it represents the only oral agent in late-stage clinical development and the only product candidate to demonstrate a survival benefit in a randomized study.

In December 2009, Cyclacel reported interim results from an ongoing Phase II study involving 60 patients aged 70 or older with either untreated AML [80%] or AML in first relapse [20%] randomized across three dosing schedules of sapacitabine [ClinicalTrials.gov Identifier NCT00590187].  The three-day dosing schedule in Arm C was selected for further clinical development in elderly patients with de novo AML based on a 1-year survival rate of 30% and an overall response rate of 35%.

In the first quarter of 2010, Cyclacel submitted a SPA request for a randomized, registration-directed, Phase III study of sapacitabine in elderly patients with AML and, pending the response, expects to initiate a pivotal Phase III study in 2010.

Summary

While many companies are developing therapies for AML [see Table 2], there is a need to focus on better frontline therapies for elderly patients given the lack of efficacy and significant toxicity associated with the current 7+3 treatment regimen.  Investors will be watching the following catalysts to help handicap which of the five product candidates [decitabine, azacitidine, clofarabine, sapacitabine, or lintuzumab] will win the race and become the first agent approved by the FDA in this setting:

• Phase IIb results for lintuzumab expected in the August to October 2010 timeframe
• FDA response to SPA request for Phase III study of sapacitabine; initiation of pivotal Phase III study in 2010
• Supplemental new drug application [sNDA] for decitabine by March 31, 2011 and subsequent response from FDA
• Results from frontline clofarabine clinical trials by AML experts and major cooperative leukemia investigation groups in the United States and Europe; relapsed/refractory AML Phase III results in 2011
• Phase III results for azacitidine expected around 2013

NEW – Click here to view this article in PDF format.

Table 2. Late-stage Therapeutic Landscape for AML

References

[i] Kantarjian H, Ravandi F, O’Brien S, Cortes J, Faderl S, Garcia-Manero G, Jabbour E, Wierda W, Kadia T, Pierce S, Shan J, Keating M, Freireich EJ.  Intensive chemotherapy does not benefit most older patients (age 70 years or older) with acute myeloid leukemia. Blood. 2010 Jul 28. [Epub ahead of print]

[ii] Amadori S, Suciu S, Willemze R, Mandelli F, Selleslag D, Stauder R, Ho A, Denzlinger C, Leone G, Fabris P, Muus P, Vignetti M, Hagemeijer A, Beeldens F, Anak O, De Witte T; EORTC leukemia group; GIMEMA leukemia group.  Sequential administration of gemtuzumab ozogamicin and conventional chemotherapy as first line therapy in elderly patients with acute myeloid leukemia: a phase II study (AML-15) of the EORTC and GIMEMA leukemia groups.  Haematologica. 2004 Aug;89(8):950-6.

[iii] Edlin R, Connock M, Tubeuf S, Round J, Fry-Smith A, Hyde C, Greenheld W.  Azacitidine for the treatment of myelodysplastic syndrome, chronic myelomonocytic leukaemia and acute myeloid leukaemia. Health Technol Assess. 2010 May;14 Suppl 1:69-74.

[iv] Eric J. Feldman, Joseph Brandwein, Richard Stone, Matt Kalaycio, Joseph Moore, Julie O’Connor, Nancy Wedel, Gail J. Roboz, Carole Miller, Raj Chopra, Joseph C. Jurcic, Randy Brown, W. Christopher Ehmann, Philip Schulman, Stanley R. Frankel, Daniel De Angelo, David Scheinberg.  Phase III Randomized Multicenter Study of a Humanized Anti-CD33 Monoclonal Antibody, Lintuzumab, in Combination With Chemotherapy, Versus Chemotherapy Alone in Patients With Refractory or First-Relapsed Acute Myeloid Leukemia. Journal of Clinical Oncology, Vol 23, No 18 (June 20), 2005: pp. 4110-4116.

With more than 200 abstracts being presented on the topic, the meeting provided an opportunity to validate some of the conclusions from our recent “Graft Versus Host Disease: Failures and Future Opportunities” article.  In particular, we reviewed data presented during the meeting and interviewed several experts in the area of Graft-versus-Host disease [GvHD] to reconfirm our three key findings:

1. Treatment of GvHD remains a large, unmet medical need
2. Low-risk, steroid-sparing approaches are favored in the short-term
3. High-risk strategies with immunomodulatory agents have been prone to failure

Unmet Medical Need

According to the National Marrow Donor Program, approximately 20,000 allogeneic hematopoietic cell transplants [bone marrow, peripheral blood hematopoietic cells, or cord blood transplants] are performed annually worldwide.  Despite the use of prophylactic therapies, GvHD still develops in 30%-80% of patients in the second month following transplant. 

 “A typical complication of patients who have a transplant with a related or an unrelated donor is GvHD of the mouth, esophagus, etc.,” said bone marrow transplant survivor Susan Stewart with BMT InfoNet, a not-for-profit organization that provides information and support services to patients that are going through transplant or have survived a transplant as well as their family members and their donors.  “It’s a serious complication – very hard to manage, very painful – so any topical or enteric medication that becomes available to help reduce it or the pain or the actual incidence of the complication is very welcome.”

While steroids, including prednisone, remain the gold standard therapy for GvHD treatment, only 25% to 41% of patients treated have complete GvHD remission.  In addition, systemic treatment with prednisone or other steroids can lead to severe side effects and mortality.

“The root cause of the biology of GvHD still is a work in progress so that unless and until we can find a particular pathway to knock out, then what we’ll be doing is probably knocking out more immune system pathways then is needed to control GvHD,” said Keith M. Sullivan, M.D., James B. Wyngaarden Professor of Medicine, Division of Cellular Therapy at Duke University Medical Center.  “Steroids for example, just knock about everything in its path down and thus the likelihood for increased infections and complications.”

While the use of prednisone is designed to suppress the T-cell mediated immune onslaught on the host tissues, it can raise the risk of infections and cancer relapse.  For example, systemic treatment with steroids is associated with increased opportunistic infections, which are caused by bacteria, fungi or viruses that do not normally cause infections in people with healthy immune systems.  Systemic steroid use may also reduce the graft-versus-tumor effect and increase the risk of cancer relapse.

“Some people will definitely relapse from their original disease and die, but many people will die from GvHD because their immune system is compromised in order to control the GvHD,” said Ms. Stewart.  “In order to control the GvHD you have to put them on immunosuppressive drugs.  That makes them susceptible to opportunistic infections and they die.”

Currently, no therapies are approved by the United States Food and Drug Administration [FDA] for either prevention or treatment of GvHD.  GvHD represents a growing problem due to an increasing number of allogeneic hematopoietic cell transplants procedures.  As a result there is an urgent need to find therapies for this disease.

“Is this an important area of continued investigation of new therapies for control and prevention of GvHD, the answer is yes,” added Dr. Sullivan.

Low Risk Approaches

Soligenix, Inc. (SNGX)

In view of how little is known about the biology of GvHD, lower-risk, steroid-sparing approaches have a higher likelihood of success in the short-term given the complexity of the disease based on our recent discussions with key opinion leaders.

In this regard, Soligenix, Inc. (SNGX), which sponsored a GvHD working committee in connection with the 2010 BMT Tandem Meetings, is developing orBec® [oral beclomethasone dipropionate] for the treatment of acute  gastrointestinal [GI] GvHD.  Beclomethasone [BDP] is a corticosteroid with potent topical activity used for inflammatory disorders affecting mucosal surfaces, such as the GI tract.  While oral BDP’s mechanism of action is similar to other corticosteroids, it does not enter into the circulation thus avoiding many of the aforementioned negatives associated with systemic steroid uses.

“In 30 years worth of controlled trials for acute GvHD treatment, there is only one agent in two publications, two different trials, that has shown an advantage of controlling GvHD and an advantage of improving survival, and that agent is oral beclomethasone,” said Dr. Sullivan.

Formulated for oral administration as a single product, orBec is a single product consisting of two separate pills.  One tablet is intended to release BDP in the upper portions of the GI tract, and the other tablet is intended to release BDP in the lower portions of the GI tract.  This novel delivery system ensures that BDP is delivered to the entire GI tract – an important competitive advantage.

“There are two phenotypes of the disease, there’s what I call the upper gut phenotype, which is 60-70% of all GvHD – people just lose their appetites, can’t eat, start getting nauseated and in the severe case have a lot of vomiting,” said George B. McDonald, MD, Professor of Medicine, University of Washington School of Medicine and Head, Gastroenterology/Hepatology Section, Fred Hutchinson Cancer Research Center.  “Then there’s the mid gut phenotype, with lots of diarrhea and intestinal ulceration and bleeding.  These two phenotypes appear to me as different sorts of diseases.  The upper gut phenotype is what the orBec is being aimed at, which is the dominant phenotype in gut GvHD.”

In a prior Phase III trial with orBec, the primary endpoint was the “time to GvHD treatment failure through study day 50,” which included a 10-day induction period of high-dose prednisone, noted David M. Hockenbery, M.D., Member, Division of Clinical Research, Fred Hutchinson Cancer Research Center, and Professor, Department of Medicine, University of Washington.  Unfortunately, twice as many prednisone “failures” during the initial 10 days of the trial counted against orBec and the primary endpoint was not achieved [p=0.1177].  By designating the first 10 days of treatment as a guarantee period, the risk of GvHD treatment failure by study day 50 was statistically significantly reduced for the orBec group relative to placebo (p=.009).  For the entire 80-day study period in the prior Phase III trial, the risk of treatment failure was statistically significantly reduced for patients in the orBec group relative to placebo (p=.02) and even further strengthened in an analysis using the 10-day guarantee period (p=.001).

“You have data suggesting that this is very effective, it’s very safe, and our mortality data from two different randomized trials showed that this approach, which spares prednisone, reduces mortality by 45%,” said Dr. McDonald.  “Two different randomized trials with the identical mortality result.  So, if you use less prednisone, you have less cytomeglaovirus, less mold infections, less bacteremia, and for some reason that still escapes me the FDA didn’t view that as a hard enough endpoint.”

In October 2009, Soligenix began enrolling patients in a confirmatory, pivotal Phase III trial under a special protocol assessment [SPA] cleared by the FDA.  The European Medicines Agency also agreed that should the new confirmatory Phase III study produce positive results, the data would be sufficient to support a marketing authorization approval in all 27 European Union member states.  The primary endpoint for this new study, treatment failure rate at day 80, is more clinically relevant and was statistically significant in the prior Phase III trial [p=0.005]. 

Soligenix has partnered with Sigma-Tau Pharmaceuticals, Inc. for commercialization of orBec, which is now the only product candidate for the treatment of acute GvHD in active Phase III development.

High Risk Approaches

Osiris Therapeutics, Inc. (OSIR)

During the 2010 BMT Tandem Meetings, Osiris Therapeutics, Inc. (OSIR) presented results from its Phase III trial evaluating Prochymal, a preparation of adult mesenchymal stem cells, for the treatment of steroid-refractory acute GvHD [abstract #41].  In September 2009, Osiris Therapeutics announced that neither of its two Phase III trials evaluating Prochymal for the treatment of GvHD achieved its primary endpoint.  There was no statistical difference between Prochymal and placebo for the steroid-refractory (35% vs. 30%, n=260) or first-line GVHD trials (45% vs. 46%, n=192), which did not come as a surprise to some researchers. 

“We participated in the mesenchymal stem cell trials, which were negative, and the dog mesenchymal stem cell studies done here were totally negative, so I don’t think we’re particularly surprised that the human studies were negative,” said Dr. McDonald.  “The model that best mimics human GvHD is the dog model, whereas the mouse models have given lots of false leads.  Mouse GvHD, in the intestine in particular, is not the same as human GvHD and things that look marvelous in the mouse, for example keratinocyte growth factor, failed miserably in human trials.  So I think there is a word of caution there about transposing animal species results to human beings.”

However, in patients with steroid-refractory liver GVHD, treatment with Prochymal significantly improved response [76% vs. 47%, p=0.03, n=61] and patients treated with Prochymal had significantly less progression of liver GvHD compared to placebo [37% vs. 65%, p=0.05].  While Osiris Therapeutics previously disclosed plans to file an amendment with the FDA to its current expanded access program, broadening the entry criteria to include patients with severe GvHD of the liver, some physicians expressed skepticism about the significance of liver GvHD.

“For GvHD, the three primary target organs are the skin, the liver, and the gastrointestinal tract,” said Dr. McDonald.  “Severe liver GvHD has become a thing of the past and that’s largely because of a drug called ursodeoxycholic acid [ursodiol], which is a bile acid that hepatologists use for cholestatic liver disease.  It’s almost completely wiped out liver GvHD.”

Indeed, previously published results [Blood. 2002 Sep 15;100(6):1977-83] demonstrated that treatment with ursodiol reduced hepatic problems and severe acute GvHD and improved survival.  Among the patients given ursodiol, the survival at one year was significantly better, 71% versus 55% (P =.02), and the non-relapse mortality rate was lower, 19% versus 34% (P =.01), than in the control group.

“There was a highly statistically significant lowering of mortality in the Nordic Study Group’s ursodiol trial,” said Dr. McDonald.  “So, if you’re not using that therapy and you’re doing trials aimed at liver GvHD I think there’s some ethical issues there, I mean there’s a way of preventing it that’s way simpler than mesenchymal stem cells.”

Celgene Corporation (CELG)

These same alloreactive donor T cells that cause GvHD can provide a beneficial graft-versus-tumor effect.  Because regulatory T cells [Tregs] have been shown to suppress GvHD while preserving the graft-versus-tumor effect, their use in the allogeneic transplant setting may represent a promising strategy to treat GvHD.   

“Back in the day, 30 years ago, it was assumed that the reason people got cured of end stage leukemia with a hematopoietic stem cell transplant was because of the massive doses of chemotherapy and sometimes radiation that is given upfront,” said Dr. McDonald.  “We’ve now discovered that is only half of it.  Most of the leukemia killing comes from what’s called a graft-versus-tumor effect.  That is, the donor cells that are causing GvHD are also seeking out leukemia and leukemia stem cells and immunologically curing the leukemia.”

During the 2010 BMT Tandem Meetings, Celgene Corporation (CELG) presented data [abstract #383] demonstrating that administration of the company’s DNA methyltransferase inhibitor azacitidine [Vidaza®] after allogeneic stem cell transplant dramatically reduced GvHD while maintaining both donor engraftment and a potent graft-versus-tumor effect in a murine bone marrow transplant model.  While the results provide a foundation for future human clinical trials, recall Dr. McDonald’s caution that the model that best mimics human GvHD is the dog model, whereas the mouse models have given lots of false leads.

Conclusion

Based on a review of data presented at the 2010 BMT Tandem Meetings and our discussions with several experts in the area of GvHD, we believe that the disease remains a large, unmet medical need.  Among the novel agents currently in clinical development, low-risk, steroid-sparing approaches are favored in the short-term as opposed to high-risk strategies with immunomodulatory agents that have been prone to failure.  Future results from Soligenix’s ongoing pivotal trial could provide optimism for both patients and investors in the GvHD space.

Disclosures:

Keith M. Sullivan, M.D., is a scientific advisor to Soligenix, Inc. and investigator in the pivotal Phase III trial.

George B. McDonald, M.D., is the inventor of orBec, Chair of Soligenix’s North American Medical Advisory Board, and maintains an equity position in Soligenix.