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