TH-302 Development: In the Shadow of the Competition

After declines in the first half of the week, shares of Threshold Pharmaceuticals (NASDAQ:THLD) rebounded on Thursday morning following an update on the company’s ongoing Phase 2 trial of TH-302 (403 Trial) in soft tissue sarcoma. The drug in combination with doxorubicin demonstrated a median progression free survival (PFS) of 6.7 months, a median overall survival (OS) of 21.5 months, and an acceptable safety profile. In a single-arm component of the study (roughly half of the total patient population) patients continued treatment with TH-302 as a single agent following the doxorubicin combination treatment; median PFS was 3.7 months, and median OS was 18.0 months in the maintenance extension. The Phase 2 supports the ongoing Phase 3 ‘406 Trial’, in which TH-302 plus doxorubicin is being compared to doxorubicin alone as a first-line soft tissue sarcoma treatment; interim data is expected in 1H13. That trial is being carried out under a Special Protocol Assessment with the FDA.

Threshold bears the brunt of upcoming trial results from multiple competitors. TH-302 is also in development as a treatment for pancreatic cancer, and last Friday, Celgene (NASDAQ:CELG) released preliminary results from a Phase 3 trial (MPACT) assessing Abraxane combined with gemcitibane as a therapy for advanced pancreatic cancer. The trial met it’s primary endpoint, improvement in overall survival, with statistical significanc,e although the company gave few details besides. On Monday, Clovis Oncology’s (NASDAQ:CLVS) drug for pancreatic cancer (CO-101) failed to produce an OS benefit in pancreatic cancer patients, and development was discontinued. And Ziopharm Oncology (NASDAQ:ZIOP) will report top-line data from its own soft tissue sarcoma drug, palifosfamide, by year’s end, and ahead of THLD’s data in 2013. (Read more about palifofsamide.) Investors focus primarily on these two TH-302 indications, which could have negative implications for THLD.

Competition in the segment, particularly as Threshold is slightly behind in the development process, will likely pressure THLD until Celgene reveals full data from Abraxane’s MPACT trial in January, just two months away. It could be a make or break moment, as Threshold and partner Merck (NYSE:MRK) have yet to begin a Phase 3 trial for TH-302 in pancreatic cancer, and may change strategies if Abraxane proves impressive. Add to that Ziopharm’s impending data release for soft tissue sarcoma and THLD faces significant headwind in the near-term; quality data from either will be negative for Threshold shares. THLD’s rally on Thursday (6% at the open) retraced losses that began on Monday, but by late morning the stock gave up most of those gains.