Ziopharm Oncology has reported positive top line interim data from the multicenter randomised phase II trial of palifosfamide (ZymafosTM, ZIO-201) treating patients with unresectable or metastatic soft tissue sarcoma. Reportedly, the analys has evaluated 62 patients treated as of the end of September, with 58 being analysed. As a result of reaching a key efficacy milestone and following safety and efficacy data review by the data committee, sarcoma experts, and the company’s medical advisory board, the decision was reached formally to stop enrollment in the trial.
The company is expected to report the interim data in full at the upcoming Connective Tissue Oncology Society (CTOS) Annual Meeting on Fifth November and plans to initiate a registration trial following regulatory review of the palifosfamide program to date.
The company has said that the randomised phase II trial treats patients with unresectable or metastatic soft tissue sarcoma in the front- and second-line setting. Patients are randomised either to doxorubicin (the current only FDA approved agent in sarcoma) or to palifosfamide in combination with doxorubicin. A total of 58 patients have been evaluated for PFS (progression-free survival) with 19 documented PFS events (doxorubicin alone = 13 events; palifosfamide + doxorubicin = 6 events) based on a three month median follow-up time. With this analysis based on all randomized and eligible patients, the hazard ratio is 0.67 favoring palifosfamide + doxorubicin (two-sided Wilcoxon-Gehan p-value = 0.042); the pre-defined milestone was to reach one-sided p=0.1.
Moreover, the interim safety data indicate that the addition of palifosfamide does not add to the toxicity of single agent doxorubicin. Robert Maki, president of CTOS (Connective Tissue Oncology Society), said: “The hypothesis of the randomized Phase II trial design for this very difficult to treat cancer population has been validated and the interim results are promising and supportive of a pivotal trial.”