First-in-human Intravesical Delivery of Pembrolizumab Identifies Immune Activation in Bladder Cancer Unresponsive to Bacillus Calmette-Guérin

Abstract

Background: Intravenous immune checkpoint inhibition is an effective anticancer strategy for bacillus Calmette-Guérin (BCG)-unresponsive non-muscle-invasive bladder cancer (NMIBC) but may be associated with greater systemic toxicity compared with localized therapies.

Objective: We assessed the safety and antitumor activity of intravesical pembrolizumab combined with BCG.

Design, setting, and participants: A 3 + 3 phase 1 trial of pembrolizumab + BCG was conducted in patients with BCG-unresponsive NMIBC (NCT02808143).

Intervention: Pembrolizumab was given intravesically (1-5 mg/kg for 2 h) beginning 2 weeks prior to BCG induction until recurrence. Urine profiling during treatment and spatial transcriptomic profiling of pre- and post-treatment tumors were conducted to identify biomarkers that correlated with response.

Outcome measurements and statistical analysis: Safety and tolerability of immune checkpoint inhibition were assessed, and Kaplan-Meier survival analysis was performed.

Results and limitations: Nine patients completed therapy. Median follow-up was 35 months for five patients still alive at the end of the trial. The trial was closed due to the COVID-19 pandemic. Grade 1-2 urinary symptoms were common. The maximum tolerated dose was not reached; however, one dose-limiting toxicity was reported (grade 2 diarrhea) in the only patient who reached 52 weeks without recurrence. One death occurred from myasthenia gravis that was deemed potentially related to treatment. The 6-mo and 1-yr recurrence-free rates were 67% (95% confidence interval [CI]: 42-100%) and 22% (95% CI: 6.5-75%), respectively. Pembrolizumab was detected in the urine and not in blood. CD4+ T cells were significantly increased in the urine after treatment, and a transcriptomic analysis identified decreased expression of T-cell exhaustion markers in late recurrences.

Conclusions: We demonstrate that intravesical pembrolizumab is safe, feasible, and capable of eliciting strong immune responses in a clinical setting and should be investigated further.

Patient summary: Direct application of pembrolizumab to the bladder is a promising alternative for non-muscle-invasive bladder cancer unresponsive to Bacillus Calmette-Guérin and should be investigated further.

Keywords: Bacillus Calmette-Guérin; Bladder cancer; Clinical trial; Digital spatial profiling; Intravesical pembrolizumab.

Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.

Figures

Figure 1:. Clinical trial design.

A) Treatment schema with dosing schedule of pembrolizumab (MK-3475) and BCG at each stage of the clinical trial. B-E) Kaplan-Meier curves showing B) Recurrence-free survival for the entire cohort (n=9) C) Recurrence-free survival by dose cohort (Cohort 1 at 1 mg/kg, and Cohort 2 at 2 mg/kg) D) Progression-free survival and E) Overall survival for the entire cohort.

Figure 2:. Progressive remodeling of local immune contents over the course of treatment by urine analysis of immune cells and cytokines

A) CD45+ cell number in the urine at baseline prior to start of treatment. B) Composition of immune cells in the urine at baseline and 2 weeks after administration of single dose of pembrolizumab. C) Changes in immune cell population in the urine during the induction period (Week 0–5). Each bar represents mean of indicated immune cells for each group. (n=4 for Late responders, n=5 for Early responders).

Figure 3:. Changes in the tumor microenvironment as a consequence of therapy

A) PCA plot showing individual region of interest (ROI) profiled from pre- and post-Tx tumor sections. B) Heatmap showing transcriptomic subtypes identified for each PanCK+ ROI within the cohort. C) Gene expression programs identified in PanCK+ segments pre- and post-treatment (Tx). D) Immune scores calculated from PanCK− segments for each analyzed sample. Bars represent Mean ± SEM. E) Immune cell counts within the tumor microenvironment derived by deconvolution of PanCK− RNA expression profiles of pre- and post-Tx ROIs (Top). Bars represent Mean ± SEM. Representative images shown for pre- and post-Tx groups (Bottom).

Figure 4:. Differences in transcriptional programs in tumor and TME from early and late responders

A) Gene expression programs identified in pre-treatment PanCK+ ROIs from early and late recurrences. B) Gene expression programs identified in pre-treatment PanCK− ROIs from early and late recurrences. C) Radar plot of Immune cell distribution in PanCK− pre-Tx ROIs from early and late responding tumors. Each point represents mean values. (p-values from comparing immune cell populations in early vs late recurrences were generated using Kruskal-Wallis test) D) Changes in Immune score and Exhaustion score for each PanCK− ROI pre-to-post treatment segregated by early and late responders.