Phase I trial of intravesical Bacillus Calmette-Guérin combined with intravenous pembrolizumab in recurrent or persistent high-grade non-muscle-invasive bladder cancer after previous Bacillus Calmette-Guérin treatment.

Objectives: We conducted the first phase I dose-escalation trial (NCT02324582) of intravesical Bacillus Calmette-Guérin (BCG) in combination with systemic pembrolizumab in patients with high-grade non-muscle-invasive bladder cancer (HGNMIBC) who had persistent or recurrent disease after prior intravesical therapy with BCG. The primary endpoint was the safety of this combination. The secondary endpoint was clinical activity at three months following BCG treatment.

Methods: Eighteen patients were consented for the study, five of which were screen failures. Six doses of pembrolizumab were administered every 3 weeks over 16 weeks concurrently with six weekly doses of BCG beginning at week 7. Patient safety was evaluated from the time of consent through 30 days following pembrolizumab treatment. Clinical activity was determined using cystoscopy and biopsy of suspicious lesions.

Results: Treatment-related adverse events included one grade 4 adverse event (AEs) (adrenal insufficiency). There were nine grade 3 AEs (chest discomfort, pulmonary embolism, arthritis, wrist edema, injection site reaction, bilateral wrist pain, cardiomyopathy, hypokalemia, urinary tract infection). There were 49 grade 1 and 30 grade 2 AEs (88% of AEs). Eleven patients finished the treatment, and two patients died during the study. Of 13 patients treated, nine patients (69%) had no evidence of disease at 3 months following BCG treatment.

Conclusions: We report for the first time that combining BCG and pembrolizumab in treating HGNMIBC is safe allowing complete treatment of most patients. A phase III trial has opened to test the efficacy of this combination in HGNMIBC (KEYNOTE-676).