Shares in Swedish biotech RhoVac were down 94% in mid-morning trading today after the company revealed a phase 2b trial of its prostate cancer vaccine RV001 showed it was no more effective than placebo.
In the 180-subject BRaVac trial, treatment with RV001 (onilcamotide) was unable to top placebo in preventing disease progression among patients who had curative therapy for localised prostate cancer but subsequently saw a rise in levels of PSA, a biomarker for recurrence.
The trial started in 2019 after RhoVac reported encouraging results in a phase 1/2 trial of RV001 in 22 subjects who received 11 subcutaneous injections with the immunotherapy over 30 weeks.
At the end of the study 18 of them (86%) had an immunological response to the shots, which is intended to treat or prevent metastasis by stimulating a T cell response to a protein called RhoC that has been implicated in tumour spread.
RhoC overexpressed in cancer cells that are prone to spreading compared with healthy cells across multiple cancer types, raising the hope that RV001 could be a broadly useful, tumour agnostic treatment for cancer.
The phase 1/2 results showed that patients treated with RV001 had PSA levels suppressed for an extended period, up to three years at last count, but that has not translated to a clinical improvement in the phase 2b study.
RV001 was not better at placebo in preventing the combined endpoint of either a doubling of PSA, clinical recurrence, or death, said RhoVac in a statement.
The company said it will now look more closely at the results and will deliver “a clear plan on how to proceed” by the end of June, which will include cost-cutting measures.
It also acknowledged that the BRaVac results mean there is “little hope of a license or acquisition deal,” something that it had suggested could follow the readout of the study if positive.
Its primary strategy was to develop RV001 to proof-of-concept stage before securing a partnership agreement or sale, so as to generate returns for shareholders, and there are no other projects mentioned in its development pipeline.
“Even though we know that benchmarks state that the probability of success for a phase II project in oncology is less than 50% and that clinical development is always a calculated risk, we are surprised and deeply saddened to find that BRaVac failed to meet its primary endpoint,” said RhoVac’s chief executive Anders Månsson.
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