Pharmexa has decided to stop further patient enrolment in its PrimoVax Phase III trial of GV1001 for pancreatic cancer (PC) after a preliminary analysis showed no survival benefit for the vaccine. The decision does not affect the company's other Phase III trial, Telovac, which is currently recruiting patients at sites in the UK.
PrimoVax was designed to investigate the use of GV1001, a peptide vaccine targeting telomerase, administered before chemotherapy in 520 patients with non-resectable PC. The study had enrolled approximately 360 subjects and was being conducted at 77 hospitals in ten European countries, as well as Australia and the US. The trial had a primary endpoint of survival, while secondary endpoints included time-to-progression and safety.
The patients in the PrimoVax trial were randomly divided into two equally sized groups: half received standard treatment with gemcitabine and half received GV1001. If the condition of the patients in the second group deteriorated, treatment with gemcitabine was added. Preliminary data based on the deaths of 174 patients showed that the survival was no better in the GV1001 group compared to the group that received gemcitabine treatment. The final conclusions with respect to survival and all secondary endpoints must await the further follow-up of patients and full analyses of the data.
The PrimoVax trial was designed as a continuation of a previous Phase I/II study with GV1001, which showed that monotherapy treatment with the vaccine significantly prolonged patient survival, compared to the effect previously seen with gemcitabine. However the Phase III results suggest that the vaccine is not best utilised in this setting.
According to Pharmexa's Chief Executive Officer, Jakob Schmidt: "It has been an open question from the start whether GV1001 should be administered before chemotherapy, as in the PrimoVax trial, or during or after chemotherapy as in the Telovac trial. We now know that giving it first does not improve overall survival in non-resectable PC patients. The focus going forward will be to show that GV1001 has a role in combination with chemotherapy and we have therefore decided to continue our support of the Telovac trial."
In contrast to the PrimoVax study, Telovac is investigating combination gemcitabine and capecitabine therapy with concurrent and sequential chemo-immunotherapy using GV1001 in patients with locally-advanced or metastatic PC. It is hoped that these two different treatment schedules will provide information as to the best time to administer the vaccine. In addition, Pharmexa is not wholly shouldering the responsibility for the trial. The study is being supported by the UK National Cancer Research Institute (NCRI) and the Pancreas Cancer Sub-Group of the NCRI, and is funded by Cancer Research UK through the Liverpool Cancer Trials Unit. Pharmexa pays for vaccine for the study and a part of the costs related to monitoring and data collection.
Early immunomonitoring data in the Telovac trial has demonstrated the immunostimulation of the vaccine, supporting the choice of scheduling and confirming the notion that immune therapies will be maximally effective when combined with treatments that cause apoptosis, such as chemotherapy. Pharmexa will be hoping that this is the case, now that its eggs concerning GV1001 are firmly in one basket.
Matthew Dennis - Editor, Cancer Drug News
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