Kosan Biosciences has discontinued its Phase II clinical trial of KOS-862 in hormone refractory prostate cancer (the KOS-202 trial). Although clinical activity was observed, based on the predefined criteria of the two-stage Simon trial design, the interim analysis of the data revealed that KOS-862 did not meet the trial's endpoint for the number of patients with a response to therapy, as measured by change in a tumour marker (Prostate Specific Antigen) levels.
The Phase II monotherapy breast cancer clinical trial continues to enrol patients, and preliminary data have been accepted for presentation at the San Antonio Breast Cancer Symposium in December 2005. The Phase Ib portion of the KOS-862 plus herceptin trial has completed enrolment, with the Phase II component of the trial is expected to initiate enrolment this quarter, informs a company release.
"While we are disappointed that the prostate trial will not proceed, we are encouraged by the potential of KOS-862 as a monotherapy and in combination with other standard chemotherapeutics in patients with breast cancer," said Daniel V. Santi, chairman and chief executive officer of Kosan.
The release further states that the KOS-202 trial was conducted in patients with advanced hormone refractory prostate cancer that had previously progressed on docetaxel-based therapy for metastatic disease. Patients received KOS-862 as single-agent therapy, with PSA response assessed every 4 weeks. Based on the data from the interim analysis, the toxicity profile in the KOS-202 trial was not dissimilar to the profile observed in the Phase II clinical trial of KOS-862 in non-small cell lung cancer. However, there was a higher incidence of adverse events resulting in patient withdrawal in the prostate cancer trial. Complete data from the KOS-202 trial is expected to be presented in the first half of 2006.
KOS-862 is a polyketide that inhibits cancer cells by the same mechanism as taxanes (paclitaxel and docetaxel), and preclinical models have shown the compound to be effective against taxane-resistant tumours. In addition to the Phase II monotherapy trial in breast cancer, Roche and Kosan are evaluating KOS-862 in three Phase Ib combination studies with gemzar, paraplatin and herceptin.
Roche and Kosan initiated their global development and commercialisation agreement for KOS-862 and other compounds in the epothilone class in September 2002. According to the agreement, Roche has the worldwide exclusive right to market and sell KOS-862 and epothilone analogs owned by or licensed to Kosan for the treatment of cancer; Kosan will co-develop and has the right to co-promote Kosan/Roche epothilone products in the U.S. for the treatment of cancer.