Long-Term Outcomes in KEYNOTE-052: Phase II Study Investigating First-Line Pembrolizumab in Cisplatin-Ineligible Patients With Locally Advanced or Metastatic Urothelial Cancer

PURPOSE

The phase II single-arm KEYNOTE-052 study evaluated the efficacy and safety of first-line pembrolizumab for patients with locally advanced or metastatic cisplatin-ineligible urothelial carcinoma (UC).

PATIENTS AND METHODS

Three hundred seventy patients received pembrolizumab 200 mg intravenously every 3 weeks for up to 24 months. Positive tumor programmed death ligand 1 (PD-L1) expression was defined as combined positive score (CPS) ≥ 10. Response was assessed by independent central review every 9 weeks per RECIST v1.1. The primary end point was objective response rate (ORR).

RESULTS

At data cutoff (September 26, 2018), the minimum follow-up was 2 years since the last patient enrolled. ORR was 28.6% (95% CI, 24.1% to 33.5%); 33 patients (8.9%) and 73 patients (19.7%) achieved complete and partial response, respectively. The median duration of response was 30.1 months (95% CI, 18.1 months to not reached [NR]); responses lasted ≥ 12 and ≥ 24 months in 67% and 52% of patients, respectively. Forty patients with complete or partial response completed 2 years of study treatment, and 32 had ongoing response at completion. Median overall survival (OS) was 11.3 months (95% CI, 9.7 to 13.1 months), and 12- and 24-month OS rates were 46.9% and 31.2%, respectively. In patients with CPS ≥ 10, ORR was 47.3% (95% CI, 37.7% to 57.0%) and median OS was 18.5 months (95% CI, 12.2 to 28.5 months). In patients with lymph node-only disease, ORR was 49.0% (95% CI, 34.8% to 63.4%), and median OS was 27.0 months (12.4 months to NR). There were no new safety signals.

CONCLUSION

First-line pembrolizumab confers meaningful and durable clinical response in cisplatin-ineligible patients with advanced UC and is associated with prolonged OS, particularly with PD-L1 CPS ≥ 10 and lymph node-only disease.

A phase II, randomized study of nivolumab (NIVO), NIVO plus linrodostat mesylate, or NIVO plus intravesical bacillus Calmette-Guerin (BCG) in BCG-unresponsive, high-risk, nonmuscle invasive bladder cancer (NMIBC): CheckMate 9UT

TPS5090

Background: Immune checkpoint inhibitors, including NIVO (anti–PD-1), have demonstrated favorable tolerability and efficacy profiles, ushering in a new treatment (tx) paradigm for advanced bladder cancer (advBC). However, an unmet need exists for new effective tx options in earlier stages of disease, specifically for patients (pts) with BCG-unresponsive, high-risk NMIBC. Increased IDO and PD-L1 expression in NMIBC tumors (Inman, et al. Cancer 2007; Hudolin, et al. Anticancer Res 2017), support the combination of anti–PD-1 and IDO1 inhibition in NMIBC. Linrodostat mesylate, a selective, potent, once-daily IDO1 inhibitor, has demonstrated clinical activity in combination with NIVO in pts with immunotherapy-naive advBC who received ≥ 1 prior line of therapy (objective response rate, 37%; Tabernero, et al. J Clin Oncol 2018;36(suppl) [abstr 4512]). Furthermore, high levels of PD-L1 expression have been reported in patients not responding to BCG tx. These findings provide a rationale for investigation of NIVO ± linrodostat ± intravesical BCG therapy in BCG-unresponsive high-risk NMIBC. Here we describe a phase 2, randomized, open-label study assessing the safety and efficacy of NIVO ± linrodostat ± intravesical BCG in pts with BCG-unresponsive, high-risk NMIBC (NCT03519256). Methods: Pts aged ≥ 18 years with BCG-unresponsive (per February 2018 FDA guidance), high-risk NMIBC, defined as carcinoma-in-situ (CIS) with or without papillary component, any T1, or Ta high-grade lesions, will be enrolled. Pts must have urothelial carcinoma as the predominant histological component ( > 50%). Key exclusion criteria include locally advanced or metastatic BC, upper urinary tract disease within 2 years, prostatic urethral disease within 1 year, and prior immunotherapy. Using a novel adaptive-type design, pts will be randomized to 1 of 4 tx arms with NIVO ± linrodostat ± BCG. Primary endpoints include proportion of pts with CIS with complete response (CR) and duration of CR in pts with CIS. Secondary endpoints are progression-free survival and safety. This global study in 14 countries is underway, with a target enrollment of 436 pts. Clinical trial information: NCT03519256 .

Pembrolizumab as First-line Therapy in Cisplatin-ineligible Advanced Urothelial Cancer (KEYNOTE-052): Outcomes in Older Patients by Age and Performance Status

Background:

Patients with treatment-naive advanced urothelial cancer (UC) Ineligible for cisplatin-based chemotherapy are typically older and have comorbidities, representing a difficult-to-treat population.

Objective:

To evaluate the safety and antitumor activity of first-line pembrolizumab in subgroups of cisplatin-ineligible older patients (aged ≥65 and ≥75 yr) with advanced UC in KEYNOTE-052 (NCT02335424), including those with poor performance status (Eastern Cooperative Oncology Group performance status score 2 [ECOG PS2]).

Design, setting, and participants:

Patients were cisplatin ineligible, had treatment-naive, histologically/cytologically confirmed, locally advanced/metastatic UC with measurable disease (Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST v1.1]), and had ECOG PS0–2. Patient subgroups analyzed were aged ≥65 yr (n = 302), ≥75 yr (n = 179), ≥65 yr with ECOG PS2 (≥65 yr + ECOG PS2; n = 119), and ≥75 yr + ECOG PS2 (n = 78).

Intervention:

All patients received pembrolizumab 200 mg intravenously every 3 wk until confirmed progression, intolerable toxicity, patient withdrawal, or 24 mo of therapy.

Outcome measurements and statistical analysis:

The primary endpoint was objective response rate (ORR) as per RECIST v1.1. The key secondary endpoints were overall survival (OS), duration of response (DOR), and safety.

Results and limitations:

ORRs for the ≥65 yr, ≥75 yr, ≥65 yr + ECOG PS2, and ≥75 yr + ECOG PS2 subgroups were 29%, 27%, 29%, and 31%, respectively; rates of complete and partial responses were similar across subgroups (9%, 5%, 6%, and 6%, and 20%, 22%, 23%, and 24%, respectively). Median DOR and OS were also consistent across the ≥65 yr and ≥65 yr + ECOG PS2 subgroups and the ≥75 yr and ≥75 yr + ECOG PS2 subgroups. Study limitations included open-label design, lack of a comparator group, and nature of post hoc exploratory analysis.

Conclusions:

The clinical benefit of pembrolizumab in advanced UC appeared to be consistent regardless of age and/or poor performance status.

This study looked at whether older age and poorer performance status affect how well patients with previously untreated advanced urothelial cancer ineligible for standard-of-care treatment respond to pembrolizumab. Outcomes with pembrolizumab were not affected by older age or poorer performance status, making it an effective option.

Randomized Double-Blind Phase II Study of Maintenance Pembrolizumab Versus Placebo After First-Line Chemotherapy in Patients With Metastatic Urothelial Cancer

PURPOSE

Platinum-based chemotherapy for first-line treatment of metastatic urothelial cancer is typically administered for a fixed duration followed by observation until progression. "Switch maintenance" therapy with PD-1 blockade at the time of chemotherapy cessation may be attractive for mechanistic and pragmatic reasons.

PATIENTS AND METHODS

Patients with metastatic urothelial cancer achieving at least stable disease on first-line platinum-based chemotherapy were enrolled. Patients were randomly assigned double-blind 1:1 to switch maintenance pembrolizumab 200 mg intravenously once every 3 weeks versus placebo for up to 24 months. Patients with disease progression on placebo could cross over to pembrolizumab. The primary objective was to determine the progression-free survival. Secondary objectives included determining overall survival as well as treatment outcomes according to PD-L1 combined positive score (CPS).

RESULTS

Between December 2015 and November 2018, 108 patients were randomly assigned to pembrolizumab (n = 55) or placebo (n = 53). The objective response rate was 23% with pembrolizumab and 10% with placebo. Treatment-emergent grade 3-4 adverse events occurred in 59% receiving pembrolizumab and 38% of patients receiving placebo. Progression-free survival was significantly longer with maintenance pembrolizumab versus placebo (5.4 months [95% CI, 3.1 to 7.3 months] v 3.0 months [95% CI; 2.7 to 5.5 months]; hazard ratio, 0.65; log-rank P = .04; maximum efficiency robust test P = .039). Median overall survival was 22 months (95% CI, 12.9 months to not reached) with pembrolizumab and 18.7 months (95% CI, 11.4 months to not reached) with placebo. There was no significant interaction between PD-L1 CPS ≥ 10 and treatment arm for progression-free survival or overall survival.

CONCLUSION

Switch maintenance pembrolizumab leads to additional objective responses in patients achieving at least stable disease with first-line platinum-based chemotherapy and prolongs progression-free survival in patients with metastatic urothelial cancer.

Expression of nectin-4 in bladder cancer with variant histology

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Background: The antibody-drug conjugate enfortumab vedotin is poised to change the bladder cancer (BC) treatment landscape by targeting Nectin-4, near ubiquitously expressed in urothelial cancer (UC). Less is known about this and other targets in BC with pure or mixed variant histology (VH). Methods: Immunohistochemistry (IHC) was performed on a Ventana Discovery Autostainer (Roche Diagnostics) using an ultraView DAB detection kit (Roche Diagnostics) and a Nectin-4 polyclonal antibody (1:100 dilution; Abcam, Cambridge, UK). The intensity and extent of Nectin-4 expression was determined by the histochemical scoring (H-score) used in preclinical testing, defined as the sum of the products of the staining intensity (score of 0–3) x % of cells (0–100) stained at a given intensity. Specimens were assessed by H score as: negative (0–14), weak (15–99), moderate (100–199), and strong (200–300). Results: Forty UC and VH BC were evaluated for Nectin-4 expression by IHC: 15 small cell (SCBC) (8 pure SCBC, 6 mixed SCBC/UC, 1 SCBC/CIS), 8 carcinosarcomas (CS) (7 pure CS, 1 HGUC/sarcomatoid features), and 17 pure HGUCs. Normal urothelium and stroma were negative. Eight of 8 (100%) pure SCBC were negative for Nectin-4. Six of 7 (85.3%) mixed SCBC+HGUC/CIS had weak staining and 1/7 (14.7%) had moderate staining in the urothelial components (comp) while 7/7 (100%) of the SCBC comp were negative. Seven of 7 (100%) pure CS were negative and 1/1 (100%) mixed CS+HGUC showed weak staining in the HGUC comp while the sarcomatoid comp was negative. Expression in UC was: 1/17 (5.9%) strong, 3/17 (17.6%) moderate, 10/17 (58.8%) weak, and 3/17 (17.6%) negative. Gene expression profiling confirmed Nectin-4 was downregulated in VH compared to UC samples, as was ERBB2 and Trop2. Conclusions: There is heterogeneity of expression of Nectin-4 and other targets in BC with VH compared to UC. This may have therapeutic implications, and highlights need for additional research in VH.[Table: see text]

Feasibility of digital pathology of circulating tumor cells with morphologic analysis in localized bladder cancer

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Background: Circulating tumor cells (CTCs) are promising biomarkers in metastatic urothelial cancer (UC). Unfortunately, efforts in localized disease have been unsuccessful, in part due to limitations of existing technologies that rely on counting cells and epithelial-marker expression. Here, we applied a novel selection-free digital pathology platform in a localized UC cohort. To date, this platform has associated CTC morphology with differential therapeutic response in metastatic UC and castrate-resistant prostate cancer. If feasible in localized UC, we may potentially identify best candidates for adjuvant therapy or bladder sparing, as well as enable sensitive monitoring for recurrence. Methods: N=16 consecutive UC pts included 8 (50%) metastatic controls and 8 (50%) localized (3 (37%) at TURBT and 5 (63%) at cystectomy). Peripheral blood was processed with the Epic CTC platform (pan-CK/CD45/PD-L1/DAPI staining). Approximately 3 million cells per slide were imaged. Unsupervised clustering categorized CTCs into 5 subtypes based on 11 morphologic features (nuclear solidity, speckling, nucleoli and entropy; cytokeratin speckling and ratio; and cytoplasmic/nuclear circularity, area, and convex area ratio). Results: 119 CTCs were detected from 11/16 (69%) pts (5/8 (63%) localized (2 NMIBC, 6 MIBC) and 6/8 (75%) metastatic). All MIBC pts had cystectomy (4/6 (67%) received NAC). 2/8 (25%) metastatic pts had stable disease, 3/8 (38%) were progressing, and 3/8 (38%) had newly detected M1. Median (range) CTC count/mL was similar for localized and metastatic pts (0.4 (0-58.6), 0.75 (0-1.9)). CTCs were detected in a pt with CIS, but not in a pt with TaHG disease. 1/16 (6.3%) pts had a single PD-L1+ CTC. CTCs were successfully assigned into 5 subtypes with predominant features of large, small, or linear cells, high cytoplasmic circularity, and prominent nucleoli. Conclusions: Digital pathology and subtype assignment of CTCs is feasible in localized UC. Ongoing efforts at our center include application of this technology in localized patients receiving investigational checkpoint inhibitor therapy to potentially predict best responders or conversely those at the highest risk for recurrence.

Molecular characterization of neuroendocrine bladder cancer

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Background: Neuroendocrine bladder cancer (NEBC) is a rare and aggressive variant that is associated with poor survival outcomes. Because NEBC is rare, the molecular features of NEBC remain poorly characterized. Therefore, we characterized NEBC at the molecular level to understand the underlying biology and identify novel therapeutic targets. Methods: Whole transcriptome RNAseq was performed on FFPE cores from 24 NEBCs and 51 conventional muscle-invasive bladder cancers (MIBCs) from Tenon Hospital in Paris. Results: Unsupervised cluster analysis of 75 tumors generated 2 distinct clusters that separated NEBCs from MIBCs. The NEBC tumors were strongly enriched with biomarkers for the characteristic of neuroendocrine or small cell malignancies, including DLL3, SOX2, and EZH2. In addition, E2F1 pathway is significantly enriched due to the impair of RB/p53 pathways. Further, the NEBCs were enriched with the TCGA’s neuronal differentiation genes that were associated with high response rates in patients treated in atezolizumab (anti-PDL1) within the context of the ImVigor 210 trial. Nevertheless, the NEBCs were characterized by suppressed immune pathway gene expression signatures, such as the Th1 pathway, effector T cell lymphocyte, and IFNg that are usually highly enriched in tumors that are sensitive to immune checkpoint blockade. Of candidate mechanisms, the suppressed TGFbpathway activity observed in the NEBCs was the most obvious explanation for sensitivity to checkpoint blockade. Conclusions: NEBCs are distinct from conventional MIBCs by gene expression signature. They are also characterized by overexpression of canonical neuroendocrine markers and inhibition of TGFb pathway activity.

INTACT: Phase III randomized trial of concurrent chemoradiotherapy with or without atezolizumab in localized muscle invasive bladder cancer—SWOG/NRG1806

TPS586

Background: Chemoradiotherapy(CRT) is a SOC for patients with muscle invasive bladder cancer (MIBC) who refuse or are not fit for radical cystectomy. Radiotherapy and chemotherapy are known to increases the PD-L1 expression in bladder cancer. Based on these observations, we hypothesized that addition of atezolizumab to CRT will increase its efficacy. Methods: This is a randomized phase III trial testing CRT with and without atezolizumab for 6 months in 475 patients with MIBC. Pts will be stratified on performance status (0-1 vs. 2); clinical stage (T2 vs T3/T4a, chemotherapy(cisplatin vs 5FU+mitomycin vs gemcitabine); and radiation field (bladder only vs small pelvis). Patients will undergo biopsy 18 week from registration. If they have residual disease they will be taken off protocol treatment and can proceed with alternative SOC option including radical cystectomy. Patients will be followed for 5 years. The primary end point of the study is bladder intact event –free survival (BIEFS). The event is comprised of: recurrence or residual muscle-invasive bladder cancer at 18 weeks or later, clinical evidence of nodal or metastatic disease, radical cystectomy, or death due to any cause. This composite endpoint is reflective of the intent of bladder preservation strategy with radical cystectomy included as one of the outcomes. Secondary end points include overall survival, modified event free survival, pathologic response at 18 weeks, metastasis free survival, cancer specific survival, rate of salvage cystectomy, rate of adverse event and QOL & PRO end points. The expected 3 year BIEFS for the control arm is 52%. The study leadership concluded that a 12% improvement in this endpoint is meaningful for this patient population. With a sample size of 475 patients the study has 85% power to detect the improvement from 52% to 64% in the BIEFS at 3 years (hazard ratio=0.68). The study team will perform translational studies evaluating tumor tissue, whole blood and urine for molecular and immunologic markers of immune response and response to RT. Successful completion of this trial could lead to a new treatment paradigm for patients with muscle invasive bladder cancer. Clinical trial information: NCT03775265.

Urothelial Cancers with Small Cell Variant Histology Have Confirmed High Tumor Mutational Burden, Frequent TP53 and RB Mutations, and a Unique Gene Expression Profile

Although predominantly urothelial, some bladder cancer and upper tract urothelial cancer (BC/UTUC) harbor histologic variants. Small cell BC (SCBC) variants comprised ˜5% of The Cancer Genome Atlas BC cohort, with a poor prognosis. We describe genomic profiles of BC/UTUC with small cell/neuroendocrine features identified in the Foundation Medicine database from June 2012 to September 2018. Of 3368 BC/UTUC samples, 3.92% (132) harbored small cell/neuroendocrine features by immunohistochemistry. Mutations were noted in: TP53 (92%), RB1 (75%), combined TP53/RB1 (72%), and TERT promoter (68%). Of the samples, 6.5% had TMB ≥ 10 mutations/Mb. RNA expression profiling of 24 pure SCBC and 51 urothelial BC (UBC) muscle-invasive samples evaluated from a separate cohort revealed a large number of differentially expressed genes with suppression of several inflammatory pathways in SCBC compared with UBC. This largest reported SCBC dataset to date confirms enrichment of signatures in SCBC similar to small cell lung cancer and describes unique gene expression compared with UBC. These findings may explain aggressive SCBC phenotype. PATIENT SUMMARY: Small cell bladder cancer (SCBC) is an aggressive subtype that microscopically resembles aggressive small cell lung cancer (SCLC). This study confirms that SCBC shares DNA changes similar to SCLC and that SCBC expresses many genes that urothelial bladder cancer does not, possibly explaining aggressive SCBC activity.

Naturally-Occurring Invasive Urothelial Carcinoma in Dogs, a Unique Model to Drive Advances in Managing Muscle Invasive Bladder Cancer in Humans

There is a great need to improve the outlook for people facing urinary bladder cancer, especially for patients with invasive urothelial carcinoma (InvUC) which is lethal in 50% of cases. Improved outcomes for patients with InvUC could come from advances on several fronts including emerging immunotherapies, targeted therapies, and new drug combinations; selection of patients most likely to respond to a given treatment based on molecular subtypes, immune signatures, and other characteristics; and prevention, early detection, and early intervention. Progress on all of these fronts will require clinically relevant animal models for translational research. The animal model(s) should possess key features that drive success or failure of cancer drugs in humans including tumor heterogeneity, genetic-epigenetic crosstalk, immune cell responsiveness, invasive and metastatic behavior, and molecular subtypes (e.g., luminal, basal). Experimental animal models, while essential in bladder cancer research, do not possess these collective features to accurately predict outcomes in humans. These key features, however, are present in naturally-occurring InvUC in pet dogs. Canine InvUC closely mimics muscle-invasive bladder cancer in humans in cellular and molecular features, molecular subtypes, immune response patterns, biological behavior (sites and frequency of metastasis), and response to therapy. Thus, dogs can offer a highly relevant animal model to complement other models in research for new therapies for bladder cancer. Clinical treatment trials in pet dogs with InvUC are considered a win-win-win scenario; the individual dog benefits from effective treatment, the results are expected to help other dogs, and the findings are expected to translate to better treatment outcomes in humans. In addition, the high breed-associated risk for InvUC in dogs (e.g., 20-fold increased risk in Scottish Terriers) offers an unparalleled opportunity to test new strategies in primary prevention, early detection, and early intervention. This review will provide an overview of canine InvUC, summarize the similarities (and differences) between canine and human InvUC, and provide evidence for the expanding value of this canine model in bladder cancer research.

Pivotal Trial of Enfortumab Vedotin in Urothelial Carcinoma After Platinum and Anti-Programmed Death 1/Programmed Death Ligand 1 Therapy

PURPOSE

Locally advanced or metastatic urothelial carcinoma is an incurable disease with limited treatment options, especially for patients who were previously treated with platinum and anti–programmed death 1 or anti–programmed death ligand 1 (PD-1/L1) therapy. Enfortumab vedotin is an antibody–drug conjugate that targets Nectin-4, which is highly expressed in urothelial carcinoma.

METHODS

EV-201 is a global, phase II, single-arm study of enfortumab vedotin 1.25 mg/kg (intravenously on days 1, 8, and 15 of every 28-day cycle) in patients with locally advanced or metastatic urothelial carcinoma who were previously treated with platinum chemotherapy and anti–PD-1/L1 therapy. The primary end point was objective response rate per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 by blinded independent central review. Key secondary end points were duration of response, progression-free survival, overall survival, safety, and tolerability.

RESULTS

Enfortumab vedotin was administered to 125 patients with metastatic urothelial carcinoma. Median follow-up was 10.2 months (range, 0.5 to 16.5 months). Confirmed objective response rate was 44% (95% CI, 35.1% to 53.2%), including 12% complete responses. Similar responses were observed in prespecified subgroups, such as those patients with liver metastases and those with no response to prior anti–PD-1/L1 therapy. Median duration of response was 7.6 months (range, 0.95 to 11.30+ months). The most common treatment-related adverse events were fatigue (50%), any peripheral neuropathy (50%), alopecia (49%), any rash (48%), decreased appetite (44%), and dysgeusia (40%). No single treatment-related adverse events grade 3 or greater occurred in 10% or more of patients.

CONCLUSION

Enfortumab vedotin demonstrated a clinically meaningful response rate with a manageable and tolerable safety profile in patients with locally advanced or metastatic urothelial carcinoma who were previously treated with platinum and anti–PD-1/L1 therapies.

EV-201: Results of enfortumab vedotin monotherapy for locally advanced or metastatic urothelial cancer previously treated with platinum and immune checkpoint inhibitors

4505

Background: Locally advanced or metastatic urothelial cancer (la/mUC) remains a lethal disease with limited treatment options for patients (pts) who progress on or after platinum and/or checkpoint inhibitor (CPI). Enfortumab vedotin (EV) is an antibody-drug conjugate targeting Nectin-4, which is highly expressed in UC. EV-201 is a pivotal, single-arm, two-cohort study of EV in la/mUC patients with prior CPI and platinum-containing chemotherapy (Cohort 1) or a CPI and no prior chemotherapy (Cohort 2). Here, we present preliminary data from Cohort 1. Methods: Pts in this open-label, multicenter study received 1.25 mg/kg EV on Days 1, 8, and 15 of each 28-day cycle. The primary endpoint was confirmed ORR per RECIST 1.1 by blinded independent central review. Secondary endpoints are duration of response, PFS, OS, safety/tolerability. Results: Between Oct 2017 and Jul 2018, EV-201 enrolled 128 pts in Cohort 1 (la/mUC pts previously treated with platinum and a CPI), 125 of whom were treated with EV (70% male; median age 69 y [range 40–84 y]; 34% upper tract; a median of 2 prior systemic therapies). As of 03 Jan 2019, the confirmed ORR was 42% (95% CI: 33.6%–51.6%), with 9% CR. The ORR in CPI non-responders was 38% (95% CI: 27.3%–49.2%), and 36% (95% CI: 22.9%–50.8%) in pts with liver metastases (LM). Most common treatment-related AEs, as determined by investigators, included fatigue (50%), alopecia (48%), and decreased appetite (41%). Treatment-related AEs of interest include any rash (48% all grade, 11% ≥ G3) and any peripheral neuropathy (50% all grade, 3% ≥ G3). One death was reported as treatment related by the investigator (interstitial lung disease), but was confounded by a suspected pulmonary infection. Conclusions: Preliminary results from this EV pivotal study demonstrated a clinically meaningful ORR, consistent with the phase 1 trial, in la/mUC pts with prior platinum and CPI, including LM pts, where there is a high unmet need. EV was well tolerated with a manageable safety profile in these pts. Updated data, including duration of response, PFS, and OS will be presented. Clinical trial information: NCT03219333.

Treatment sequencing of anti-PD-1/PD-L1 and carboplatin (carbo)-based chemotherapy (chemo) in cisplatin-ineligible patients (pts) with metastatic urothelial cancer (mUC)

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Background: Anti-PD-1/PD-L1 agents and carbo-based chemo are therapy options in 1st-line (1L) setting for cisplatin-ineligible pts with mUC. However, optimal sequencing is unclear. Methods: We conducted a multicenter retrospective analysis of cisplatin-ineligible pts with mUC treated with 1L PD-1/PD-L1 monotherapy followed by carbo-based chemo (IO→Cb) or the reverse order (Cb→IO) without intervening systemic therapy. Perioperative cisplatin-based chemo was allowed if completed > 1 year from 1L mUC therapy initiation. To assess association between overall survival (OS) and therapy sequence, a multivariate analysis (MVA) was performed from initiation of 2L therapy, adjusted for treatment sequence, time interval between initiation of 1L and 2L therapies, Hb ( < 10 vs ≥10 g/dl), ECOG PS (0-1 vs 2-3), and metastatic site (LN/soft tissue only vs non-liver vs liver). Results: 146 pts (IO→Cb n = 43, Cb→IO n = 103) were evaluable with median age 72, 76% men, 78% ECOG PS 0-1, 17.8% with liver metastasis. Baseline factors were balanced except for higher proportion of men in IO→Cb group (91% vs 70%, p = 0.01). Median time interval between initiation of 1L and 2L therapy for IO→Cb and Cb→IO were 15.6mo (4.8-78.1) and 23.0mo (2.1-103.3), respectively. Response rates are summarized (Table). On MVA, treatment sequence was not associated with OS (HR 1.05, p = 0.85). Site of metastasis was the only factor significantly associated with OS (p = 0.002). Conclusions: In our retrospective analysis of cisplatin-ineligible pts with mUC regardless of PD-L1 expression, anti-PD-1/PD-L1 followed by carbo-based chemo or the reverse sequence appeared to confer comparable OS. The observed response rates and time interval between initiation of 1L and 2L therapy are likely contributed by pt selection, where all pts received 2L. Further investigation of the ‘PD-L1 high’ population is warranted, given higher response rates with anti-PD-1/PD-L1 vs ‘PD-L1 low’ population. Ongoing phase III trials will help inform optimal sequencing. [Table: see text]

Bacillus Calmette-Guerin (BCG) with or without pembrolizumab (pembro) for high-risk (HR) nonmuscle invasive bladder cancer (NMIBC) that is persistent or recurrent following BCG induction: Phase III KEYNOTE-676 study

TPS4591

Background: Intravesical instillation of BCG is standard of care for patients (pts) with HR NMIBC. However, many pts have persistent/recurrent HR NMIBC after BCG induction and are at increased risk for progression to muscle-invasive disease. Interim data from the phase 2 KEYNOTE-057 study has shown that the PD-1 inhibitor pembro had promising efficacy in HR NMIBC as monotherapy. KEYNOTE-676 (NCT03711032) is a randomized, comparator-controlled, phase 3 trial to evaluate efficacy and safety of pembro plus BCG in pts with persistent/recurrent HR NMIBC after BCG induction therapy. Methods: Pts are randomly assigned 1:1 to continue BCG therapy alone or receive BCG plus pembro 200 mg every 3 weeks. Treatment is stratified by carcinoma in situ (CIS) histology (presence/absence), PD-L1 combined positive score (≥10/˂10), and timing of NMIBC persistence/recurrence (0 to ≤6, ˃6 to ≤12, or ˃12 to ≤24 mo). Pts are eligible if they are ≥18 years of age with histologically confirmed persistent/recurrent HR NMIBC of the bladder after adequate BCG induction therapy, have undergone cystoscopy/transurethral resection of bladder tumor within 12 weeks before randomization, have no concurrent extravesical disease, and have an ECOG PS score of 0-2. Responses are assessed by cystoscopy and blinded independent central review of urine cytology and biopsy (as applicable) every 12 weeks for years 1-2 and every 24 weeks for years 3-5 and by computed tomography urography every 18 months through year 5. Treatment will continue with pembro for up to 2 years and BCG for 3 years or until confirmed HR NMIBC persistence, recurrence, or disease progression, unacceptable toxicity, or pt/physician decision to withdraw. Primary end point is complete response rate in pts with CIS. Secondary end points are event-free survival (EFS), recurrence-free survival, overall survival, disease-specific survival, time to cystectomy, 12-month EFS rate in all pts, duration of response (DOR), 12-month DOR rate in pts with CR and safety and tolerability. Recruitment began in November 2018 and will continue until ~550 pts are enrolled. Clinical trial information: NCT03711032.

KEYNOTE-052: Phase 2 study evaluating first-line pembrolizumab (pembro) in cisplatin-ineligible advanced urothelial cancer (UC)— Updated response and survival results

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Background: Initial results of the phase 2 KEYNOTE-052 (NCT02335424) study led to approval of pembro for cisplatin-ineligible patients (pts) with advanced UC. Updated results representing follow-up of over 2 y since last pt enrolled are presented. Methods: Pts had confirmed advanced UC, were cisplatin-ineligible (ECOG PS 2, CrCl ≥30 to ˂60 mL/min, grade ≥2 neuropathy/hearing loss, NYHA Class III heart failure), and received no prior chemotherapy for metastatic disease. Pts received pembro 200 mg IV Q3W until progression, unacceptable toxicity, withdrawal, or 24 mo of therapy, whichever occurred first. Primary end point was confirmed ORR (RECIST v1.1, independent central review). Key secondary end points: duration of response (DOR), overall survival (OS), and safety. Data cutoff was September 26, 2018. Results: Among pts assessed (N = 370), median age was 74 y, 85% had visceral disease, and 30% were PD-L1 positive (combined positive score [CPS] ≥10). Median follow-up was 11.4 mo (range, 0.1-41.2) for all pts and 29.3 mo (range 7-41.2) for responders. Confirmed ORR was 29% (95% CI, 24-34): complete response, 9% (n = 33); partial response, 20% (n = 73). Median DOR was 30.1 mo (95% CI, 18.1-not reached [NR]); 67% and 52% of pts had DOR ≥12 and ≥24 mo, respectively. Median OS was 11.3 mo (range 9.7-13.1); 12- and 24-mo OS rates were 47% and 31%, respectively. In pts with CPS ˂10 (n = 251) and ≥10 (n = 110), respectively, confirmed ORR was 20% (95%CI, 16-26) and 47% (95% CI, 38-57). Median DOR for pts with CPS < 10 and ≥10 was 18.2 mo (95% CI, 9.7-NR) and NR (95% CI, 18.1-NR); DOR ≥24 mo was 45% and 57%, respectively. Median OS for pts with CPS < 10 and ≥10 was 9.7 mo (95% CI, 7.6-11.5) and 18.5 mo (95% CI, 12.2-28.5); 24-mo OS rates were 24% and 47% respectively. Treatment-related adverse events (AEs) occurred in 67% of pts. Most common were fatigue and pruritus (18% each); 21% were grade ≥3, including 1 death (myositis). Conclusions: With extended follow-up, pembro continued to elicit clinically meaningful, durable antitumor activity in cisplatin-ineligible pts with advanced UC and was more pronounced in those with PD-L1 expression CPS ≥10. Pembro safety profile was as expected. Clinical trial information: NCT02335424.

Randomized double-blind phase II study of maintenance pembrolizumab versus placebo after first-line chemotherapy in patients (pts) with metastatic urothelial cancer (mUC): HCRN GU14-182

4504

Background: Platinum-based chemotherapy for 1st-line treatment of pts with metastatic urothelial cancer (mUC) is typically administered for a fixed duration followed by observation until recurrence. PD-1 blockade with pembro improves survival of pts with mUC progressing despite platinum-based chemotherapy. We explored the potential benefit of earlier use of PD-1 blockade using a "switch maintenance" approach. Methods: Pts with mUC achieving at least stable disease after up to 8 cycles of 1st-line platinum-based chemotherapy were enrolled. Pts were randomized 1:1 to pembro 200 mg IV q3 weeks versus placebo for up to 24 months; pts progressing on placebo could cross over to pembro. Randomization was stratified based on pre-chemotherapy visceral metastases (Y/N) and response to 1st-line chemotherapy (CR/PR vs. SD). The primary objective was to determine the progression-free survival (PFS) as per irRECIST among pts treated with pembro versus placebo. Results: Between 12/2015 and 11/2018, 107 pts were randomized to placebo (n=52) versus pembro (n=55). The baseline pt characteristics are shown in the Table. Pts randomized to placebo and pembro received a median of 6 and 8 cycles, respectively. Excluding patients with baseline CRs, the objective response rate was 12% (5/42) on placebo and 22% (10/46) on pembro. Grade 3-4 treatment emergent adverse events occurred in 48% of pts on placebo and 56% on pembro. At a median follow-up of 14.7 months, 41 pts have died and 26/52 pts randomized to placebo have crossed over to pembro. PFS was significantly longer in patients randomized to pembro vs. placebo (Maximum Efficiency Robust Test p=0.036; log-rank p = 0.038). The 18-month restricted mean progression-free survival time was 5.6 months with placebo and 8.2 months with pembro (p=0.023). Conclusions: Switch maintenance pembro may “deepen” responses achieved with 1st-line chemotherapy. Switch maintenance pembro prolongs PFS in pts with mUC completing 1st-line platinum-based chemotherapy. Clinical trial information: NCT02500121. [Table: see text]

Immunomodulation by HDAC inhibition: Results from a phase Ib study with vorinostat and pembrolizumab in metastatic urothelial, renal, and prostate carcinoma patients

2572

Background: Immunosuppressive factors such as regulatory T cells (Tregs) and myeloid-derived suppressive cells (MDSCs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been shown to have immunomodulatory effects. We have previously reported that HDAC inhibitors have synergistic antitumor effects in combination with PD-1 inhibition in tumor models by inhibiting the function of Tregs and MDSCs. Thus, we conducted a Phase Ib clinical study with the HDAC inhibitor vorinostat and the PD-1 inhibitor pembrolizumab in patients (pts) with metastatic urothelial, renal and prostate carcinoma. Methods: The primary objective was to evaluate the safety and tolerability of this combination strategy. The phase I portion consisted of two dose levels of vorinostat (100 and 200 mg, PO daily 2 weeks ON and one week OFF) and a fixed, standard dose of pembrolizumab (200 mg IV every 21 days). Patients were assigned to three cohorts: Cohort A (previously treated, anti-PD1/PD-L1 naïve urothelial and renal cancer pts = 15), Cohort B (previously treated, anti-PD1/PD-L1 resistant urothelial and renal cancer pts = 14), and Cohort C (prostate cancer pts = 14). Results: Dose levels 1 (4 enrolled, 3 evaluable) and 2 (4 enrolled, 3 evaluable) were completed without DLTs and 200 mg was the Phase II recommended dose for vorinostat. The most common resolved grade 3/4 toxicities were acute kidney injury (n = 1), anemia (n = 1), diarrhea (n = 1), and hypothyroidism (n = 1) in the dose expansion cohorts. We have enrolled 43 pts (37 evaluable) in the dose expansion cohorts. For Cohort A, B, and C the median PFS were 2.8 months, 5.2 months, and 3.5 months. Two PR were observed including the dose escalation phase. Two PCA pts have achieved undetectable PSA. We have performed several correlative studies including flow cytometry and gene expression analysis on peripheral blood mononuclear cells, PDL-1 staining and PSMA PET scans in a subset of pts. Conclusions: The results from this phase Ib suggest that the combination of vorinostat and pembrolizumab is relatively well tolerated and may be active in a subset of immune checkpoint resistant UC/RCC pts and immune checkpoint naïve PCA pts. Clinical trial information: NCT02619253.

5-factor prognostic model for survival of patients with metastatic urothelial carcinoma receiving three different post-platinum PD-L1 inhibitors

4552

Background: A prognostic model for overall survival (OS) of metastatic urothelial carcinoma (mUC) was previously reported in the setting of post-platinum atezolizumab (Pond GR, GU ASCO 2018). This model was limited by employing only atezolizumab treated patients (pts), small size of the validation dataset and unclear applicability to other PD-1/L1 inhibitors. Hence, we constructed a robust prognostic model utilizing the combined atezolizumab cohort as the discovery dataset and used 2 separate validation datasets comprised of post-platinum avelumab or durvalumab treated pts. Methods: The discovery dataset consisted of pt level data from 2 phase I/II trials (IMvigor210 and PCD4989g) evaluating atezolizumab (n = 405). Pts enrolled on 2 separate phase I/II trials, EMR 100070-001 that evaluated post-platinum avelumab (n = 242) and CD1108 that evaluated durvalumab (n = 189) comprised the validation datasets. Cox regression analyses evaluated the association of candidate prognostic factors with OS. Factors were dichotomized and laboratory values were normalized by logarithmic transformation. Stepwise selection was employed to propose an optimal model using the discovery dataset. Discrimination and calibration were assessed in the avelumab and durvalumab datasets following the validation procedure by Royston and Altman (2013). Results: The 5 factors included in the optimal prognostic model in the discovery dataset were ECOG-PS (1 vs. 0; HR 1.80; 95% CI [1.36-2.36]), presence/absence of liver metastasis (HR 1.55; 95% CI [1.20-2.00]), number of platelets (HR 2.22; 95% CI [1.54-3.18]), neutrophil-lymphocyte ratio (NLR; HR 1.94; 95% CI [1.57-2.40]) and lactate dehydrogenase (LDH; HR 1.60; 95% CI [1.28-1.99]). There was robust discrimination of survival between low, intermediate and high-risk groups based on 0-1, 2-3 and 4 factors. The concordance of survival was 0.692 in the discovery and 0.671 and 0.775 in the avelumab and durvalumab validation datasets, respectively. Acceptable or good calibration of expected 1-year survival rate was observed. Conclusions: A 5-factor prognostic model is prognostic for survival across 3 different PD-L1 inhibitors (atezolizumab, avelumab, durvalumab) in this large study totaling 836 pts overall in the setting of post-platinum therapy for mUC. This model may assist in prognostic stratification and interpreting nonrandomized trials of post-platinum PD1/L1 inhibitors.

PrE0807 phase Ib feasibility trial of neoadjuvant nivolumab (N)/lirilumab (L) in cisplatin-ineligible muscle-invasive bladder cancer (BC)

TPS4594

Background: Neoadjuvant cisplatin-based chemotherapy before radical cystectomy (RC) improves outcomes but ~50% of patients (pts) are cisplatin-unfit. Anti-PD(L)1 agents can prolong overall survival (OS) in platinum-resistant advanced BC and have shown high pathologic complete response rate (pCR) and safety as single agent in phase II trials in the neoadjuvant setting. The combination of anti-PD-1 and anti-KIR agents is feasible and very attractive based on complementary and non-overlapping roles in regulating adaptive and innate immune response as well as impacting the function CD8+ T and NK-cells. Higher CD8+ T cell density (TCD) at RC tissue correlates with longer OS. We hypothesize, that combining anti-PD1 (N) with anti-KIR (L) is safe and feasible as neoadjuvant therapy in cisplatin-unfit pts and results in high CD8+ TCD at RC. Methods: Phase Ib multi-institutional trial evaluating 2 doses (4 weeks apart) of N alone or N+L in 2 cohorts; pts will be assigned sequentially to N (Cohort 1), and if there is no negative safety signal after the first 12 pts, subsequent pts will be assigned to N+L (Cohort 2). Key eligibility: cT2-4aN0-1M0 stage, ≥20% tumor at TURBT, adequate organ function, no autoimmune disease within 2 years, no concurrent invasive upper urinary tract carcinoma or other active cancer. Primary endpoint: safety based on CTCAE v5.0 measured as the rate of ≥G3 treatment related adverse events (AE). Key secondary endpoints: CD8+ TCD absolute and % change between TURBT and RC, % of pts who do not get RC within 6 weeks after neoadjuvant treatment due to treatment-related AE, % pCR, recurrence-free survival, and evaluation of biomarkers in tumor tissue, blood, urine. Rates of ≥Grade 3 AE with neoadjuvant treatment will be reported along with 90% exact binomial CI. In Cohort 1, maximum CI width is 0.51; in Cohort 2, it is 0.36. Our hypothesis is that the change in CD8+ TCD between TURBT and RC will be about 3 CD8+ T cells / 100 tumor cells within HPF. Up to 43 pts will be enrolled for 36 eligible, treated pts (12:N, 24:N+L). Cohort 1 and 2 have 81% and 98% power, respectively, to detect the hypothesized difference with 1-sided type I error rate of 0.05. Trial is open to accrual in US. Clinical trial information: NCT03532451.

Tumor immune microenvironment in non-muscle-invasive urothelial carcinoma of the bladder

Immunotherapy has gained significance in a variety of tumor types including advanced urothelial carcinoma. Noninvasive urothelial lesions have been treated with intravesical Bacillus-Calmette-Guerin (BCG) for decades. Given treatment failure in a subset of these tumors, ongoing clinical trials investigating the role of checkpoint inhibitors are actively pursued in this group of patients. The present study aims to delineate PD-L1, CD8, and FOXP3 expression in tumor microenvironment in non-muscle-invasive urothelial carcinoma samples obtained via sequential biopsies and to assess its potential role in predicting disease outcome. Cases with >1% and> 5% PD-L1 expression in tumor cells showed lower relative risk (RR) to recur at any subsequent biopsy compared with those with lower PD-L1 expression (RRs, 0.83 [P = .009] and 0.81 [P = .03], respectively). Cases with higher expression of FOXP3 in peritumoral lymphocytes were at lower risk for tumor grade progression at any biopsy (RR, 0.2; P = .02). Tumors with FOXP3/CD8 expression ratio of >1 in intratumoral lymphocytes had lower risk of grade progression (RR, 0.28; P = .04). Although higher number of FOXP3-, CD8-, and PD-L1-positive lymphocytes were encountered after BCG treatment, the findings did not reach statistical significance. In patients without BCG treatment, PD-L1 expression in tumor cells and peritumoral lymphocytes varied across serial biopsies, suggesting the need for additional approaches to assess eligibility for immunotherapy in non-muscle-invasive urothelial carcinoma patients.

Keynote-676: Phase 3 study of bacillus calmette-guerin (BCG) with or without pembrolizumab (pembro) for high-risk (HR) non–muscle invasive bladder cancer (NMIBC) that is persistent or recurrent following BCG induction

TPS502

Background: Intravesical instillation of BCG is the standard of care for patients with HR NMIBC. However, many patients have persistent/recurrent HR NMIBC after BCG induction and are at a particularly increased risk for progression, representing a significant unmet need. Programmed cell death ligand 1 (PD-L1) expression in the tumor microenvironment may attenuate responses to BCG. KEYNOTE-676 is a randomized, comparator-controlled, phase 3 trial to evaluate the efficacy and safety of the PD-1 inhibitor pembro plus BCG in patients with persistent/recurrent HR NMIBC after BCG therapy. Methods: Adult (≥18 years) patients with histologically confirmed persistent/recurrent HR NMIBC of the bladder after adequate BCG induction therapy are eligible. Patients are required to have undergone cystoscopy/transurethral resection of bladder tumor within 12 weeks prior to randomization, to have no concurrent extravesical disease, and to have ECOG performance status score 0-2, adequate organ function, and tissue for biomarker analysis. Patients will be randomly assigned 1:1 to continue on BCG therapy alone or receive BCG plus pembro 200 mg every 3 weeks. Treatment will be stratified by carcinoma in situ (CIS) histology (presence/absence), PD-L1 combined positive score (≥10/˂10), and timing of NMIBC persistence/recurrence (0 to ≤6, ˃6 to ≤12, or ˃12 to ≤24 mo). Primary end point is complete response rate in participants with CIS. Secondary end points will include event-free survival, patient-reported outcomes, and safety. Responses will be assessed by cystoscopy and blinded independent central review of urine cytology and biopsy (as applicable) every 12 weeks for years 1-2 and every 24 weeks for years 3-5 and by computed tomography urography every 18 months through year 5. Treatment will continue with pembro for up to 2 years and BCG for 3 years or until pathology-confirmed HR NMIBC persistence, recurrence, or disease progression, unacceptable toxicity, or patient/physician decision to withdraw. Recruitment will begin November 2018 and will continue until ~550 patients are enrolled. (NCT03711032). Clinical trial information: NCT03711032.

Defining “platinum-ineligible” patients with metastatic urothelial cancer (mUC)

451

Background: Patients (pts) with mUC who are ineligible to receive cisplatin have limited treatment options. Pembrolizumab and atezolizumab were approved as 1st-line therapy in these pts, but their use is now restricted in pts with tumors with high PD-L1 expression, or platinum-ineligible. “Platinum-ineligible” mUC (cisplatin and carboplatin ineligible), remains undefined, and a clear definition is needed for determining treatment and clinical trial eligibility. Methods: We surveyed 56 genitourinary medical oncologists in the US using an online tool consisting of several clinical parameters (Round 1) and based on the responses, we refined the survey (Round 2) and then compiled the responses to generate a consensus definition. Results: Responses were received from 43/56 (77%) of those surveyed in Round 1 and 44/56 (78.5%) in Round 2. Based on the results shown in the Table, we recommend 1 of the following 5 parameters be used to define "platinum-ineligible” mUC: ECOG PS > 3; Cr Cl < 30 ml/min; Peripheral neuropathy > 3; NYHA Heart Failure Class > 3; ECOG PS 2 and Cr Cl < 30 ml/min. Conclusions: “Platinum-ineligible” mUC is a new and undefined category with a substantial definition variability among investigators. Results from consensus definition are proposed for standardization of this mUC category. [Table: see text]

A phase II, randomized study of nivolumab (nivo) or nivo plus BMS-986205 with or without intravesical Bacillus Calmette-Guerin (BCG) in BCG-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC): CheckMate 9UT

TPS493

Background: Immune checkpoint inhibitors, including nivo (anti–PD-1), have demonstrated favorable tolerability and efficacy profiles, ushering in a new treatment (tx) paradigm for advanced bladder cancer (advBC). However, an unmet need exists for new effective tx options in earlier stages of disease, specifically for patients (pts) with BCG-unresponsive, high-risk NMIBC. Increased IDO and PD-L1 expression in NMIBC tumors (Inman, et al. Cancer 2007; Hudolin, et al. Anticancer Res 2017), support the combination of anti–PD-1 and IDO1 inhibition in NMIBC. BMS-986205, a selective, potent, once-daily IDO1 inhibitor that works early in the IDO1 pathway, has demonstrated clinical activity in combination with nivo in pts with immunotherapy-naive advBC who received ≥ 1 prior line of therapy (objective response rate, 37%; Tabernero, et al. J Clin Oncol 2018;36(suppl) [abstr 4512]). These findings provide a rationale for investigation of nivo + BMS-986205 ± intravesical BCG therapy in BCG-unresponsive high-risk NMIBC. Here we describe a phase 2, randomized, open-label study assessing the safety and efficacy of nivo ± BMS-986205 ± intravesical BCG in pts with BCG-unresponsive, high-risk NMIBC. Methods: Pts aged ≥ 18 years with BCG-unresponsive (per February 2018 FDA guidance), high-risk NMIBC, defined as carcinoma-in-situ (CIS) with or without papillary component, any T1, or Ta high-grade lesions, will be enrolled. Pts must have urothelial carcinoma as the predominant histological component (>50%). Key exclusion criteria include locally advanced or metastatic BC, upper urinary tract disease within 2 years, prostatic urethral disease within 1 year, and prior immunotherapy. Using a novel adaptive-type design, pts will be randomized to 1 of 4 tx arms with nivo ± BMS-986205 ± BCG. Primary endpoints include proportion of pts with CIS with complete response (CR), duration of CR in pts with CIS, and event-free survival for all pts without CIS. Secondary endpoints are progression-free survival and safety. This global study in 13 countries is underway, with a target enrollment of 436 pts. ( Clinical trial information: NCT03519256.

Combined Next-generation Sequencing and Flow Cytometry Analysis for an Anti-PD-L1 Partial Responder over Time: An Exploration of Mechanisms of PD-L1 Activity and Resistance in Bladder Cancer

Anti-PD-L1/PD-1 immunotherapy has improved survival for certain patients with metastatic urothelial carcinoma. However, the mechanisms of resistance to these agents have not been fully elucidated. We report the first combined analysis using RNA sequencing, whole-exome sequencing (WES), and flow cytometry of multiple tumor specimens over a 5-yr period for a patient undergoing anti-PD-L1 therapy. Initial sensitivity to anti-PD-L1 immunotherapy was associated with conversion to a basal molecular subtype and a rising tumor mutational burden. We found that as the tumor became more resistant to anti-PD-L1, the proportion of regulatory T cells and CD8⁺ T cells expressing alternative immune checkpoints including CTLA-4, TIM-3, and LAG-3 increased. This suggests that alternative immune checkpoint upregulation may be one form of anti-PD-L1 resistance in urothelial carcinoma. These data support the concept of combined immune checkpoint blockade for urothelial carcinoma, a concept that is being evaluated in prospective clinical trials. PATIENT SUMMARY: In this study we characterized how a patient with metastatic urothelial cancer became resistant to anti-PD-L1 immunotherapy. By tracking changes in protein and gene expression over time, we found that as urothelial carcinoma becomes resistant to PD-L1 blockade, additional immune checkpoints may be upregulated. These data support the concept of combined checkpoint blockade for urothelial carcinoma.

Mocetinostat for patients with previously treated, locally advanced/metastatic urothelial carcinoma and inactivating alterations of acetyltransferase genes

Background

The authors evaluated mocetinostat (a class I/IV histone deacetylase inhibitor) in patients with urothelial carcinoma harboring inactivating mutations or deletions in CREB binding protein [CREBBP] and/or E1A binding protein p300 [EP300] histone acetyltransferase genes in a single‐arm, open‐label phase 2 study.

Methods

Eligible patients with platinum‐treated, advanced/metastatic disease received oral mocetinostat (at a dose of 70 mg 3 times per week [TIW] escalating to 90 mg TIW) in 28‐day cycles in a 3‐stage study (ClinicalTrials.gov identifier NCT02236195). The primary endpoint was the objective response rate.

Results

Genomic testing was feasible in 155 of 175 patients (89%). Qualifying tumor mutations were CREBBP (15%), EP300 (8%), and both CREBBP and EP300 (1%). A total of 17 patients were enrolled into stage 1 (the intent‐to‐treat population); no patients were enrolled in subsequent stages. One partial response was observed (11% [1 of 9 patients; the population that was evaluable for efficacy comprised 9 of the 15 planned patients]); activity was deemed insufficient to progress to stage 2 (null hypothesis: objective response rate of ≤15%). All patients experienced ≥1 adverse event, most commonly nausea (13 of 17 patients; 77%) and fatigue (12 of 17 patients; 71%). The median duration of treatment was 46 days; treatment interruptions (14 of 17 patients; 82%) and dose reductions (5 of 17 patients; 29%) were common. Mocetinostat exposure was lower than anticipated (dose‐normalized maximum serum concentration [C_max] after TIW dosing of 0.2 ng/mL/mg).

Conclusions

To the authors’ knowledge, the current study represents the first clinical trial using genomic‐based selection to identify patients with urothelial cancer who are likely to benefit from selective histone deacetylase inhibition. Mocetinostat was associated with significant toxicities that impacted drug exposure and may have contributed to modest clinical activity in these pretreated patients. The efficacy observed was considered insufficient to warrant further investigation of mocetinostat as a single agent in this setting.

After the genomic‐based selection of patients with urothelial cancer with inactivating mutations/deletions in the histone acetyltransferase genes CREBBP and/or EP300, single‐agent mocetinostat appears to be associated with significant toxicities that limit drug exposure. This may have contributed to the limited activity noted in the current phase 2 study (response rate of 11%) among heavily pretreated patients with platinum‐refractory disease.