Seattle Genetics at ASH 2007 - SGN-33 (part III)
Tuesday, December 25th, 2007There are currently 2 ongoing and one planned clinical trials for the evaluation of SGN-33.
The first clinical trial is the extension of the phase I trial, but this time all patients are to receive the highest dose tested in the original phase I (8mg/kg). The company expects to have data from this trial by the beginning of 2009. Typically, these types of trials should result in better performance than the first dose escalation trial, since the highest dose is expected to achieve better results than lower doses. In this case, since clinical activity in the highest dose and in the lower doses was similar, I wouldn’t expect to see a substantial improvement in the rate of CR in the ongoing trial. This can be explained by the fact that even lower doses ( 4 and 2.5 mg/kg) lead to the saturation of the vast majority of CD33 in the bone marrow, so any additional antibodies that enter the bone marrow has no targets left to bind. This is also why the dose was not escalated beyond 8 mg/kg even though there were no dose limiting toxicities.
The second trial (and the more important one) is a randomized double-blind trial where SGN-33 is combined with low-dose araC, the standard therapy for older AML patients. Half of the patients are to receive araC+ placebo with the other half receiving araC+ SGN33. This trial will hopefully shed some light on two crucial issues.
