Candel’s trial was conducted under the FDA’s Special Protocol Assessment program, meaning that its data could be used as a basis for a regulatory application.
Massachusetts biotech Candel Therapeutics on Wednesday announced that its investigational biological immunotherapy CAN-2409 hit the primary endpoint in a Phase III prostate cancer study, sending the biotech’s stocks soaring more than 200%.
The late-stage study enrolled 745 patients with intermediate-to-high-risk localized prostate cancer. In the trial’s experimental arm, patients were treated with viral immunotherapy with CAN-2409 plus the prodrug valacyclovir, on top of standard of care external beam radiation therapy, whereas controls were given standard of care plus placebo. The study’s primary endpoint was disease-free survival (DFS).
In the intent-to-treat population, CAN-2409 led to a statistically significant improvement in DFS, with a hazard ratio of 0.7 and a p-value of 0.0155, according to Candel’s news release. At 54 months, patients treated with CAN-2409 saw a 14.5% relative improvement in DFS versus placebo comparators.
CAN-2409’s DFS benefits were maintained in a subgroup analysis of patients on short-term androgen deprivation therapy (ADT) and in those who are not on ADT.
Candel’s candidate likewise aced key secondary endpoints, including prostate-specific outcomes such as prostate cancer–free survival, for which CAN-2409 achieved a “highly statistically significant” benefit, according to the biotech. There were also significantly more patients on CAN-2409 that achieved a prostate-specific antigen nadir concentration of less than 0.2 ng/mL, as compared with placebo.
Two-year biopsies showed a pathological complete response rate of 80.4% in CAN-2409-treated patients, as opposed to 63.6% in controls. The difference was statistically significant.
As for safety, Candel said that CAN-2409 was overall well-tolerated with an adverse event profile that was consistent with what had been established in prior studies. No new signals of concern were documented. The most common side effects included fever, chills and other flulike symptoms, which were mild to moderate in severity.
CEO Paul Peter Tak said in a statement that the biotech is “thrilled” with this Phase III readout, which “validates previous observations of CAN-2409 activity seen in difficult-to-treat solid tumors” and “confirms our previous observation of synergies with radiation therapy” in prostate cancer models.
The late-stage study was conducted under the FDA’s Special Protocol Assessment program, which enables companies to align with the FDA on the design and protocol of clinical trials, with an eye toward regulatory filing. “Safety and efficacy data generated from the study could be sufficient for the Company to seek regulatory approval for CAN-2409 in this indication,” Tak added.
In an analysis piece, a Seeking Alpha analyst wrote that Candel “now faces the very real possibility of having a favorable submission to the FDA by around the midpoint of 2025,” depending on how well the biotech can follow through on Wednesday’s readout. An approval could come as early as late 2025 or, more likely, in 2026, according to the analyst.
Also on Wednesday, Candel revealed that CAN-2409 had failed a Phase II trial, which assessed the asset as a monotherapy for patients with low-to-intermediate-risk localized prostate cancer patients on active surveillance. Time to radical treatment and the proportion of patients achieving negative biopsies at 1 year after dosing were numerically in favor of CAN-2409, but failed to reach statistical significance.
According to the Seeking Alpha analyst, this mid-stage failure might represent a risk for Candel and “definitely raises a little bit of concern that their drug approach works in one setting but not another that is closely related.”
