FDA Panel Votes Down Potential Bladder Cancer Immunotherapy

oligometastatic prostate cancer

Brian Rini, MD

An FDA panel voted against approval of the immunotherapy MCNA as a treatment for patients with high-risk non-muscle invasive bladder cancer (NMIBC) following first-line bacillus Calmette-Guérin (BCG) therapy. The consideration for approval stemmed from findings from the open-label phase III trial EN3348-301 (Study 301), which did not meet its primary endpoint.

The panel, which included members of the FDA's ODAC and CTGTAC committees, voted 18-6 against the treatment and concluded that the risks of MCNA outweigh the potential benefit. A final decision on MCNA is scheduled by February 27, 2016.

"I think the compound clearly has potential antitumor activity in areas in which we are desperate for more therapy ... [However] there were too many questions on the data," said Brian Rini, MD, associate professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University.

Study 301 consisted of 129 patients who were treated with an induction dose of MCNA at 8 mg weekly. The disease-free survival (DFS) rate of patients treated with MCNA was 25% at 1-year and 19% at 2-years. The primary endpoint of the study was a 1-year DFS rate of over 40%. Additionally, the FDA calculated a 1-year DFS of 20.9% using a responder landmark analysis, which was also lower than the primary endpoint. After 3 months of induction therapy, disease-free patients then received a maintenance dose from months 3 to 24. In this portion of the study, MCNA was given in 3 weekly installments every 3 months.

Of the enrolled patients, 91 had carcinoma in situ (CIS) with or without papillary disease and 38 had papillary-only tumors. An FDA review of baseline pathology reports found discrepancies between local and central pathology reports, most frequently being that central pathology identified more subjects with CIS and papillary disease. The FDA's final determination comprised 93 CIS-containing patients and 36 that were papillary only.

Most patients in Study 301 had high-risk disease, with 107 being BCG-refractory and 22 being BCG relapsing. The FDA analysis of BCG relapsing/refractory status determined an identical breakdown. At a median 34.7-month follow-up in Study 301, the median disease-free duration in responders was 32.7 months. The progression-free survival (PFS) rate at 1-year was 87.3%. At years 2 and 3, the PFS rate with MCNA was 79.8% and 77.7%, respectively.

The FDA's analysis included efficacy results among patient subgroups. Specifically, the 1-year DFS was 17% and 10%, respectively, among CIS-containing and papillary-only patients. In the CIS-containing group, the complete response rate was 27%, with a median response duration of 15.1 months. One-year DFS rates were 19% and 8%, respectively, among BCG-refractory and BCG-relapsing patients.

"I'm not convinced that his agent really changes the natural history of the disease. I don't think that the sponsor nor many of us [here today] have been able to tease out a good reference population or a good study showing what the natural history would be for this BCG refractory and/or relapsing group," Christian Pavlovich, MD, associate professor and director, Urologic Oncology, Johns Hopkins Medical Institutions said in explaining his opposition to approving MCNA.

The safety data considered during the FDA joint-committee session included 129 patients from study 301 and 37 subjects from Study 303 who received at least 1-dose of MCNA. The phase III randomized Study 303 was designed to compare MCNA with mitomycin C in patients with non-muscle invasive bladder cancer; however, the trial was stopped early in November 2012 due to logistic issues.

Ninety-two percent of patients in study 301 had at least 1 adverse event (AE) of any grade, with 14% of patients having serious AEs. There were 3 treatment-emergent deaths, but none related to MCNA instillation.

Hematuria (36.4%), dysuria (32.6%), fatigue (21.7%), UTI (19.4%), pollakiuria (17.8%), and micturition urgency (13.2%) were the most common treatment-emergent AEs with MCNA.

MCNA-related serious AEs included one grade 3 UTI and one moderate hematuria. Two patients withdrew due to MCNA-related AEs (1 asthenia and 1 vomiting).

Fifteen patients (11.6 %) enrolled in Study 301 developed metastatic bladder cancer (MBC), with days from first MCNA instillation to MBC diagnosis ranging from 239 days to 1267 days.

When combining the Study 301 and 303 populations for the overall safety analysis, the most common all-grade AE's included fatigue (15.7%), malaise (3.6%), chills (3%), pyrexia (2.4%), nausea (2.4%), diarrhea (2.4%), asthenia (2.4%), and abdominal distension (2.4%).

MCNA is an immunotherapy composed of mycobacterial cell wall fragments complexed with nucleic acids. Endo Pharmaceuticals and Bioniche Life Sciences initially developed the treatment as part of a joint collaboration. In 2012, Endo returned global rights for the medication to Bioniche, which later rebranded itself as Telesta in 2014. In June 2015, Telesta, which is based in Canada, received a patent for MCNA in the United States, providing intellectual property protection for the immunotherapy for 16 years.

As part of the submission process for MCNA, Telesta completed a number of upgrades and improvements to its manufacturing facility and operating procedures. These upgrades were completed in February 2015, prior to an FDA pre-approval inspection under their formal review process.