After six months, 69% and 73% of patients treated with TH-302/gemcitabine were still alive compared to 51% for the gemcitabine patients.
After one year, 37% and 38% of the TH-302/gemcitabine patients were still alive compared to 21% of the gemcitabine patients.
While encouraging, the new survival analysis is not without caveats. Removing crossover patients creates selection bias, meaning the improved survival benefit may not be attributable to TH-302 but instead to patients remaining in the control arm who were sicker and therefore didn't live as long. The analysis was also retrospective, meaning it wasn't conducted as part of the original design of the study -- lessening its significance.
Almost half the pancreatic patients enrolled in the Threshold study were also treated with additional drugs after TH-302 or gemcitabine stopped working. These "subsequent" therapies could have also helped patients live longer, making it even harder to tease out the survival benefit attributable to TH-302 alone.
On the safety side, TH-302 was associated with higher rates of thrombocytopenia (low platelets), neutropenia (low white blood cells) and anemia. TH-302's blood-related toxicities coupled with anticipation for upcoming results from a phase III study of
(CELG - Get Report)
Abraxane in pancreatic cancer dampened enthusiasm for TH-302 at ESMO, wrote Pieter Droppert, a cancer consultant who writes the
Biotech Strategy Blog/
: "If [Abraxane] were to increase overall survival to 10-12 months, this would become the new standard of care that TH-302 would then have to beat. Based on the TH-302 data presented at ESMO 2012, even if you ignore the hematological toxicity, this is hard to imagine from the phase II study, which is why the data failed to impress me."
The final data from the phase II study of TH-302 in pancreatic cancer presented Saturday answer some questions but raise others. Ultimately, the measure of the drug will only come after Threshold and its partner Merck KGaA conduct and complete a phase III study.
For another take on Threshold and the TH-302 data, make sure to read the latest column from
contributor Nate Sadeghi on why the
pancreatic cancer drug may be obsolete before launch
--Written by Adam Feuerstein in Boston.
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