Hammer Stock Blog

Seattle Genetics (SGEN) recently published clinical data from a phase I which evaluated SGN-33 for the treatment of elderly AML (Acute Myelogenous Leukemia) patients. AML is a common type of blood cancer, with around 13,000 new cases and 9000 deaths expected to occur during 2007 in the US alone. Prognosis of the disease is very poor, especially among elderly patients (over 60 years old), who have a long term survival rate of 5%, compared to 20% in the case of patients who are under 60. The dismal prognosis elderly AML patients have can be attributed to their inability to tolerate aggressive chemotherapy or stem cell transplant. Moreover, AML among elderly patients is inherently more resistant to standard chemotherapy due to several factors. Therefore, there is a unique challenge in developing better treatments for elderly AML patients, because these treatments must be very safe in addition to being effective. Antibodies, as well as other targeted therapies are regarded as excellent candidates, as they have an excellent safety profile and can be usually co-administered with other treatments. The market opportunity for such treatments is substantial, due to the high incidence of AML among elderly patients, so naturally there are multiple treatments currently being evaluated. The majority of these treatments are chemo agents but there are several targeted therapies, the most promising of which is SGN-33.

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A lot of clinical data was published at the American Society of Hematology (ASH) meeting, some of it quite impressive. Naturally, established drugs such as Millennium Pharmaceuticals‘ (MLNM) Velcade, Genentech’s (DNA) Rituxan and Celgene’s (CELG) Revlimid got most of the attention. In my opinion, the real star of the conference is MT-103 which is being co-developed by Micromet (MITI) and MedImmune, the biologics division of AstraZeneca (AZN). I won’t go too deep into describing the mechanism of action and the platform based on which MT-103 is built (I intend to do that in a review I hope to publish next week). However, the clinical data presented by Micromet is so impressive and so groundbreaking from several perspectives, that it must not be ignored.

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CD70 program

CD70 is a receptor expressed on many types of blood cancers as well as the majority of renal cancer cases. The expression profile of this target is highly restricted to cancer cells, which, combined with its ability to internalize antibodies, makes it a desirable target for ADCs. Seattle Genetics is evaluating a naked antibody as well as an ADC that target CD70, both candidates are based on the same antibody, which was licensed from CLB-Research and Development. The naked antibody, SGN-70, is evaluated for certain blood cancers and is expected to enter phase I during 2008. Another possible use for SGN-70 is for autoimmune diseases, as it is expressed on white blood cells that are involved in the disease, but not on “resting” cells.

SGN-75 is an ADC based on SGN-70, which is currently evaluated pre-clinically for Renal cell carcinoma. This disease, although not as common as prostate and lung cancers, represents a large market opportunity with over 43,000 new cases and almost 13,000 deaths expected in 2007 in the US alone. Although surgical resection of the kidney has high chances to prevent the disease from spreading, nearly one third of patients are diagnosed at advanced stage, where the cancer has spread to additional organs. In addition, more than 30% of patients who undergo resection will eventually develop metastatic disease, for which very few therapeutic options exist. SGN-75 is expected to enter the clinic only in 2009.

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The partnership with MedImmune, which dates back to 2005, is probably Seattle Genetics’ second most important partnership. On the scientific side, now that MedImmune has been merged with Cambridge Antibody Technology [CAT] to form AstraZeneca’s (AZN) biologics division, Seattle Genetics has a real antibody powerhouse on its side. On the financial side, Seattle Genetics could benefit from another pharma giant on its partner list, equipped with the 8th largest R&D budget in the industry and consequently the ability to support multiple clinical programs simultaneously. Looking at Immunogen’s partnership with Sanofi-Aventis, which has thus far led to 3 clinical programs, is making us hope that AstraZeneca will be to Seattle Genetics, what Sanofi is to Immunogen.

The cooperation with MedImmune originally revolved around one target – EphA2. This intriguing target is highly expressed in numerous solid cancers including breast, prostate and colorectal, which makes the potential opportunity immense. In addition, there is a growing body of scientific evidence that expression of EphA2 is associated with aggressiveness and poor survival, which makes its targeting very reasonable in advanced stages of the disease. The specific targeting of EphA2 looks particularly promising since MedImmune’s scientists discovered that there are several regions within EphA2 which become exposed and consequently accessible for antibodies only on cancer cells.

MedImmune views Epha2 as a very important target. In fact, it has such high hopes for it, that there it is currently evaluating multiple approaches to targeting this promising antigen. One of these approaches is Micromet’s (MITI) Bite (stands for: Bi-Specific T cell Engager) platform, which is being co-developed with Medimmune for several targets, one of which is EphA2. The Bite Platform, a very interesting technology (that deserves an article of its own being so different from other antibody-based platforms) consists of two small antibodies that link between a tumor and specific immune cells in order to manipulate them to attack the tumor. It has demonstrated very impressive potency in mice, and even more impressive results among heavily pre-treated NHL patients, mainly due to the very low doses that showed a clinical effect. The Bite platform hasn’t been evaluated in solid tumors yet, but clinical trials are expected to be announced in the future, one of them is for a Bite agent that targets Epha2. Due to its unique characteristics that present both advantages and disadvantages, it is very hard to predict Bite’s efficacy in these settings. Although some consider Bite an immunotoxin, it differs from immunoconjugates in that it does not contain any drug or toxin payload, so it is reasonable to expect that MedImmune will explore it in parallel to Seattle Genetics’ platform. Although Bite is not necessarily a direct competitor, I bet the folks at Seattle Genetics are following that program closely. Nevertheless, MedImmune seems pretty happy with Seattle Genetics’ platforms, as it has recently licensed Seattle Genetics’ ADC technology for a second undisclosed target.

Author is long SGEN

CR011-vcMMAE is an ADC currently being developed by Curagen (CRGN), based on Seattle Genetics’ ADC technology. The ADC comprises of an antibody against GPNMB, a protein on the surface of melanoma cells linked to a drug payload. Both the drug and the linker in this case are identical to those used by Seattle Genetics in SGN-35. The story behind this agent demonstrates the need of ADC technology and the high value it has in today’s drug development market. It also demonstrates that going after one of the most challenging indication with a relatively new platform, may not be the best way to validate it.

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SGN-35, which is Seattle Genetics’ lead ADC, is comprised of SGN-30 and Seattle Genetics’ highly toxic chemo drug – MMAE. SGN-35 is, in fact, the company’s flagship ADC candidate, since it was its first wholly owned ADC to utilize the company’s new ADC technology, including its peptide-based linker and auristatin-based drug. Having both a naked antibody and an ADC based on the same antibody simultaneously in the clinic is quite unusual, but more than anything, this situation is fascinating because it can clearly exhibit the advantages ADCs have over naked antibodies. In that sense, SGN-35 is similar to Genentech’s Herceptin-DM1, which is currently being developed with Immunogen (IMGN). Herceptin-DM1 served as a validation for Immunogen’s ADC technology since it showed very encouraging results among breast cancer patients, who do not respond to naked Herceptin. Hence, if Seattle Genetics can show that SGN-35 succeeds where SGN-30 fails (hint- Hodgkin’s Lymphoma), without causing substantial side-effects, it should be a very strong proof-of-concept.

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SGN-30 entered phase I in 2002, for the treatment of HL and ALCL. In addition to a good safety profile, SGN-30 managed to show clinical activity, mainly among ALCL patients. The antibody was advanced to a phase II trial which later turned into 2 phase II trials, one for the evaluation in HL and the other in ALCL. Results from the two phase II trials emphasized the trend that had been observed in the phase I trial, as SGN-30 demonstrated great activity among ALCL patients but very modest activity in HL. Of the 35 evaluable HL patients, there was no objective response (decrease of 30% in the tumor load), whereas, 14 out of 46 evaluable ALCL patients (30%) had a response, three of which were durable complete responses. This is quite impressive considering the poor prognosis of these heavily pretreated patients. Although SGN-30 could not beat HL, Seattle Genetics still had several options at its disposal, including an armed version of SGN-30, in which the antibody is conjugated to a drug payload.

Although it is very important to get data about an antibody as a single agent, the activity it shows in combination with existing treatments is where most of the potential lies. A typical strategy with antibodies for cancer includes initial evaluation as a single agent in patients who have no other alternatives, followed by multiple trials in combination with existing treatments and/or in early stage patients, who have better prognosis. Ideally, any drug company would like to see its drug being administered as early and in as many combinations as possible, in order to achieve maximal market share. This is indeed the case with SGN-30, which is currently being evaluated in 3 phase II combination trials.

The first study was initiated in 2006 and is evaluating SGN-30 in combination with chemotherapy for the treatment of recurrent HL. This is a relatively large, comparative trial aimed at discovering whether SGN-30 can enhance chemo’s efficacy. The second study, also initiated in 2006, is evaluating SGN-30 in combination with chemotherapy among ALCL patients. A third study of SGN-30 combined with chemotherapy is recruiting pediatric ALCL patients. These trials are financed by the NCI, which enables Seattle Genetics allocating resources to other clinical programs. Despite the promising clinical activity among ALCL patients, the addressable market for ALCL is rather limited, making its clinical development attractive but not too exciting. Obviously, as long as someone else is paying the bills, Seattle Genetics will be more than happy to see SGN-30 advance towards commercial availability, but unless there are stellar results from the HL combination trial, we expect SGN-30 to remain on the backburner, as far as Seattle Genetics is concerned. The real star in the company’s CD30 program is SGN-35.

Author is long SGEN

As we previously explained, the market for lymphomas, targeted by Rituxan is huge, and attracts many companies. There are, however, several lymphomas for which Rituxan is not effective since Rituxan’s target, the CD20 receptor, is not expressed by these cancers. These conditions, expected to be diagnosed in more than 15,000 Americans in 2007, can be divided into two groups: Hodgkin’s lymphoma [HL] and T-cell NHL [T-NHL]. Patients diagnosed with such conditions are treated with similar regimens that are used for NHL, however, Rituxan is omitted because it has no effect. Combining chemotherapy and radiotherapy with antibodies is a well validated concept, since antibodies can increase a regimen’s efficacy without substantial side effects. As there are currently no approved antibodies for the treatment of non CD-20 lymphomas, there is a great rational behind developing such antibodies that can be co administered with existing treatments. Although market opportunity for treatments for these “non Rituxan” lymphomas is substantially smaller than the Rituxan opportunity, it is still a viable niche which is poorly addressed by most players in the field. Seattle Genetics’ CD30 program is aimed specifically at that niche.

CD30 is a well known marker for Hodgkin’s Lymphoma [HL], expressed by certain malignant cells that are present in the patient’s lymph nodes. Interestingly, these cells (Reed-Sternberg cells), represent only a small portion of the tumor but are considered to be the driving force in the creation and development of the disease. In addition, CD30’s expression in normal tissues is very limited, making it ideal for antibody-based therapy. HL is one of the most curable cancers, as historical data shows that patients have a 75% chance of achieving complete remission with a combination of several chemo drugs. However, up to 40% of patients will relapse, some of which will develop chemo-resistant tumors. The most viable option for patients whose disease has relapsed is bone marrow transplant, an aggressive treatment that is associated with high incidence of mortality and low success rates in this type of patients. Interestingly, CD30 presence has been associated with aggressive disease, making anti-CD30 antibodies a very reasonable path for treating advanced stage patients. The market for HL will never become as gigantic as the NHL market, with “only” 8190 cases of HL and 1,070 HL-related deaths are expected in 2007 in the US.

CD30 is also expressed on 30% of T-NHL, most consistently on a subtype of T-cell lymphoma called anaplastic large cell lymphoma [ALCL]. Many T-NHL lymphomas, in contrast to HL, are characterized by very poor prognosis and new treatments are desperately needed. It is hard to estimate the market opportunity on this front, but it seems like it is in the scale of several thousand cases per year in the US. Seattle Genetics is currently evaluating 2 anti-CD30 platforms: SGN-30, which is a naked antibody and SGN-35 which is an antibody-drug conjugate [ADC].