A Treatment Vaccine for Low-Risk Prostate Cancer

Neil Osterweil

May 20, 2016

A Louisiana-based biopharmaceutical company is betting that its experimental immunotherapeutic vaccine can keep previously untreated prostate cancer in check.

The company, OncBioMune Pharnaceuticals, Inc, in Baton Rouge, is planning to test the vaccine, dubbed ProscaVax, in a phase 2 trial for patients with previously untreated prostate cancer and in a second trial for patients with recurrent or hormone-refractory disease.

The trial of a treatment vaccine in untreated, low-risk prostate cancer patients is novel.

"To the best of the Company's knowledge, ProscaVax will be the only cancer vaccine in the world in mid-stage clinical research evaluating safety and efficacy in prostate cancer patients in the 'active surveillance' category," an OncBioMune press release says.

Other prostate cancer treatment vaccines have been studied in advanced disease (eg, sipuleucel-T [Provenge, Dendreon Corp]) or in progressive disease.

According to the company, the vaccine contains the prostate-specific antigen (PSA) whole protein plus interleukin-2 and granulocyte macrophage–colony stimulating factor as adjuvants.

The efficacy data on the product are sparse.

In a phase 1a/1b clinical trial in men with biorecurrent or hormone-refractory disease conducted at the University of California, San Diego (UCSD), 8 of 9 patients had "an increased immune response" at 31 weeks post vaccination, and 6 of 10 patients had a "reduction" in PSA progression after receiving six doses of the vaccine, the company says.

The patients enrolled in this trial are men with early, largely asymptomatic biorecurrence after treatment (as indicated by rising PSA), explained principal investigator Gregory A. Daniels, MD, PhD, from the UCSD Moores Cancer Center.

The patients "either had chosen not to move right away onto castration, or were castration-resistant, with rising PSA but no measurable disease. That's the group we targeted, because they're generally a group we're struggling with finding the right thing for," he said in an interview with Medscape Medical News.

Although the investigators had planned to study additional doses of the vaccination in a maintenance schedule, "the data is [sic] compelling enough that OncBioMune has elected to forego the Phase 1b component and advance ProscaVax into two, separate Phase 2 studies,” the company announced.

One of the phase 2 studies will be hosted by "a major university in the Northeast United States and its network of cancer centers."

Glenn J. Bubley, MD, director of genitourinary oncology at Harvard-affiliated Beth Israel Deaconess Medical Center in Boston, has agreed to serve as principal investigator and is currently reviewing the documentation for submission to the US Food and Drug Administration (FDA), the company says.

The second phase 2 study, to be conducted in Mexico, is designed to evaluate the safety and efficacy of ProscaVax in biorecurrent prostate cancer in both hormone-naive and hormone-independent patients.

Curious Doings

An expert in immunotherapeutic cancer vaccines told Medscape Medical News that despite the company hype, this product appears to have flown largely under the radar.

David M. Lubaroff, PhD, professor of urology and microbiology and associate director of the Holden Comprehensive Cancer Center at the University of Iowa Carver College of Medicine, in Iowa City, is the principal investigator for phase 2 studies of a PSA-directed vaccine using an adenoviral vector for treatment of men with biorecurrent prostate cancer after therapy and for men with hormone-refractory disease.

"As I understand from their release, they are going to be treating patients who are currently under active surveillance who have not been treated, and this has not been tried recently," he said in an interview.

"The pushback that some people might expect is that you're treating patients who have not had any other therapy with an unknown type of therapy. The issue I would question is the level of tumor burden in these patients. Once you get a heterogeneous population of patients, all with different sizes and different grades of tumors, then you may run into problems with that," he said.

Dr Lubaroff also said that it is "curious" that there are apparently no published data, apart from sparse details included in press releases, from the early clinical trials.

A search by Medscape Medical News of the medical literature, Google, and the FDA website for published data on the vaccine turned up only press releases and a poster describing the early clinical trial designs from the 2014 annual meeting of the American Society of Clinical Oncology.

"They haven't published those results, and they're going right into a phase 2 [trial]? That's interesting," Dr Lubaroff commented.

The clinical trials are sponsored by OncBioMune. Dr Daniels and Dr Lubaroff have disclosed no relevant financial relationships.

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