CureVac has acknowledged that its prostate cancer immunotherapy vaccine candidate CV9104 failed a Phase IIb clinical trial in patients with asymptomatic or minimally symptomatic metastatic castrate-resistant forms of the disease.

Topline results showed that CV9104 failed to meet the trial’s primary endpoint of improving overall survival, CureVac said, adding that progression-free survival was similar in both the treatment and placebo arms of the placebo-controlled clinical trial.

Progression-free survival was one of two “key” secondary endpoints for the study; the other was change of quality of life.

“We now recognize that this therapeutic vaccine fails to induce a survival benefit as a monotherapy in patients with metastatic prostate cancer receiving standard-of-care therapies. However, we see the path forward for our RNActive® cancer immunotherapy in combination with checkpoint inhibitors,” Ingmar Hoerr, Ph.D., CureVac’s co-founder and CEO, said in a statement.

The Phase IIb trial assessed CV9104 in 197 chemo-naïve, asymptomatic, or minimally symptomatic patients with metastatic, castrate-resistant prostate cancer randomized to the vaccine candidate or placebo. The trial was conducted in eight European countries starting in 2012, with recruitment completed in December 2013.

CureVac said it is continuing to evaluate data from the trial and plans to present the full set of data “at an upcoming medical conference.”

CV9104 is one of two vaccine candidates using the company’s RNActive® technology for which the company disclosed results yesterday. The other candidate, the rabies vaccine CV7201, appeared well tolerated with no safety concerns identified, based on interim results, CureVac said.

In 21 subjects vaccinated at the lowest dose of 80 µg with a needle-free device, virus-neutralizing antibodies were detected in all subjects, with 17 (81%) exceeding the threshold considered protective by the World Health Organization (0.5 IU/mL). CureVac said the complete dataset will be published after completion of a long-term safety evaluation.

RNActive uses optimized antigen-encoding and complexed messenger RNA (mRNA) molecules to stimulate the immune system. By modifying the sequence of mRNA, CureVac says, the stability of the molecule is improved while translational levels are enhanced without changing the amino acid sequence of the corresponding protein.

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