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].