PURPOSE KEYNOTE-158 ( ClinicalTrials.gov identifier: NCT02628067) is a phase II basket study investigating the antitumor activity and safety of pembrolizumab in multiple cancer types. We present interim results from patients with previously treated advanced cervical cancer. PATIENTS AND METHODS Patients received pembrolizumab 200 mg every 3 weeks for 2 years or until progression, intolerable toxicity, or physician or patient decision. Tumor imaging was performed every 9 weeks for the first 12 months and every 12 weeks thereafter. The primary end point was objective response rate (ORR), assessed per Response Evaluation Criteria in Solid Tumors (version 1.1) by independent central radiologic review. Safety was a secondary end point. RESULTS Ninety-eight patients were treated. Median age was 46.0 years (range, 24 to 75 years), and 65.3% of patients had Eastern Cooperative Oncology Group performance status of 1. Eighty-two patients (83.7%) had programmed death-ligand 1 (PD-L1)–positive tumors (combined positive score ≥ 1), 77 having previously received one or more lines of chemotherapy for recurrent or metastatic disease. Median follow-up was 10.2 months (range, 0.6 to 22.7 months). ORR was 12.2% (95% CI, 6.5% to 20.4%), with three complete and nine partial responses. All 12 responses were in patients with PD-L1–positive tumors, for an ORR of 14.6% (95% CI, 7.8% to 24.2%); 14.3% (95% CI, 7.4% to 24.1%) of these responses were in those who had received one or more lines of chemotherapy for recurrent or metastatic disease. Median duration of response was not reached (range, ≥ 3.7 to ≥ 18.6 months). Treatment-related adverse events occurred in 65.3% of patients, and the most common were hypothyroidism (10.2%), decreased appetite (9.2%), and fatigue (9.2%). Treatment-related grade 3 to 4 adverse events occurred in 12.2% of patients. CONCLUSION Pembrolizumab monotherapy demonstrated durable antitumor activity and manageable safety in patients with advanced cervical cancer. On the basis of these results, the US Food and Drug Administration granted accelerated approval of pembrolizumab for patients with advanced PD-L1–positive cervical cancer who experienced progression during or after chemotherapy.

We present data from patients with advanced biliary tract cancer (BTC) receiving pembrolizumab in the KEYNOTE‐158 (NCT02628067; phase 2) and KEYNOTE‐028 (NCT02054806; phase 1b) studies. Eligible patients aged ≥18 years from both studies had histologically/cytologically confirmed incurable BTC that progressed after standard treatment regimen(s), measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, Eastern Cooperative Oncology Group performance status 0/1, and no prior immunotherapy. Programmed death ligand 1 (PD‐L1)‐positive tumors were required for eligibility in KEYNOTE‐028 only. Patients received pembrolizumab 200 mg every three weeks (KEYNOTE‐158) or 10 mg/kg every two weeks (KEYNOTE‐028) for ≤2 years. Primary efficacy endpoint was objective response rate (ORR) by RECIST v1.1. Response assessed by independent central review is reported. KEYNOTE‐158 enrolled 104 patients and KEYNOTE‐028 enrolled 24 patients. Median (range) follow‐up was 7.5 months (0.6‐34.3) in KEYNOTE‐158 and 5.7 months (0.6‐55.4) in KEYNOTE‐028. In KEYNOTE‐158, ORR was 5.8% (6/104; 95% CI, 2.1%‐12.1%); median duration of response (DOR) was not reached (NR) (range, 6.2‐26.6+ months). Median (95% CI) OS and PFS were 7.4 (5.5‐9.6) and 2.0 (1.9‐2.1) months. Among PD‐L1‐expressers (n = 61) and PD‐L1‐nonexpressers (n = 34), respectively, ORR was 6.6% (4/61) and 2.9% (1/34). In KEYNOTE‐028, ORR was 13.0% (3/23; 95% CI, 2.8%‐33.6%); median DOR was NR (range, 21.5‐53.2+ months). Median (95% CI) OS and PFS were 5.7 (3.1‐9.8) and 1.8 (1.4‐3.1) months. Grade 3 to 5 treatment‐related adverse events occurred in 13.5% of patients in KEYNOTE‐158 (no grade 4; grade 5 renal failure, n = 1) and 16.7% in KEYNOTE‐028 (no grade 4/5). In summary, pembrolizumab provides durable antitumor activity in 6% to 13% of patients with advanced BTC, regardless of PD‐L1 expression, and has manageable toxicity.

Background: Cancer immunotherapy has changed the standard of care for a subgroup of patients with advanced disease. Immune checkpoint blockade (ICB) in particular has shown improved survival compared with previous standards of care for several tumor types. Although proven to be successful in more immunogenic tumors, ICB is still largely ineffective in patients with tumors that are not infiltrated by immune cells, the so-called cold tumors.Patients and methods: This review describes the effects of different chemotherapeutic agents on the immune system and the potential value of these different types of chemotherapy as combination partners with ICB in patients with solid tumors. Both preclinical data and currently ongoing clinical trials were evaluated. In addition, we reviewed findings regarding different dosing schedules, including the effects of an induction phase and applying metronomic doses of chemotherapy.Results: Combining ICB with other treatment modalities may lead to improved immunological conditions in the tumor microenvironment and could thereby enhance the antitumor immune response, even in tumor types that are so far unresponsive to ICB monotherapy. Chemotherapy, that was originally thought to be solely immunosuppressive, can exert immunomodulatory effects which may be beneficial in combination with immunotherapy. Each chemotherapeutic drug impacts the tumor microenvironment differently, and in order to determine the most suitable combination partners for ICB it is crucial to understand these mechanisms. Conclusion:Preclinical studies demonstrate that the majority of chemotherapeutic drugs has been shown to exert immunostimulatory effects, either by inhibiting immunosuppressive cells and/or activating effector cells, or by increasing immunogenicity and increasing T-cell infiltration. However, for certain chemotherapeutic agents timing, dose and sequence of administration of chemotherapeutic agents and ICB is important. Further studies should focus on determining the optimal drug combinations, sequence effects and optimal concentration-time profiles in representative preclinical models.

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4079 Background: Antitumor activity with pembro, an anti–PD-1 antibody, has been observed in patients (pts) with advanced/metastatic biliary tract cancers (BTC), who have limited treatment options. We present follow-up data from pts with advanced BTC treated with pembro in the KN158 (NCT02628067; phase 2) and KN028 (NCT02054806; phase 1) studies. Methods: Eligible pts ≥18 y in the KN158/KN028 BTC cohorts had histologically/cytologically confirmed incurable advanced BTC that progressed after/failed any number of prior standard treatment regimens, measurable disease per RECIST v1.1, ECOG PS of 0/1, and no prior immunotherapy. PD-L1–positivity (membranous PD-L1 expression in ≥1% of tumor and associated inflammatory cells or positive staining in stroma) was required for eligibility in KN028, but not KN158. Pts received pembro 200 mg Q3W (KN158) or 10 mg/kg Q2W (KN028) for up to 2 y. Radiographic imaging occurred Q9W for 12 mo (KN158) or Q8W for 6 mo (KN028) and Q12W thereafter. Primary efficacy endpoint in both studies was ORR by RECIST 1.1. Response assessed by independent central review is reported. Results: Median (range) follow-up was 7.5 (0.6–29.5) mo in the 104 pts from KN158 and 6.5 (0.6–33.1) mo in the 24 pts from KN028 with BTC. All pts in KN028 and 61 in KN158 had PD-L1–positive tumors. No pt had MSI-H tumors (not assessed in KN028). In KN158, ORR was 5.8% (6/104, all PR [including 1 pt with PD-L1–negative tumor]; 95% CI, 2.1%–12.1%) and median duration of response (DOR) was not reached (NR; range, 6.2 to 23.2+ mo). Median OS and PFS were 7.4 mo (95% CI, 5.5–9.6) and 2.0 mo (95% CI, 1.9–2.1). 12-mo OS rate was 32.7%. In KN028, ORR was 13.0% (3/23, all PR; 95% CI, 2.8%‒33.6%) and median DOR was NR (range, 21.5 to 29.4+ mo). Median OS and PFS were 6.2 mo (95% CI, 3.8‒10.3) and 1.8 mo (95% CI, 1.4‒3.7), respectively. 12-mo OS rate was 27.6%. Grade 3–5 treatment-related AEs occurred in 13.5% in KN158 (1 pt had grade 5 renal failure) and 16.7% of pts in KN028 (no grade 5). 18.3% in KN158 and 20.8% of pts in KN028 had an immune-mediated AE or infusion reaction. Conclusions: Pembro provides durable antitumor activity, regardless of PD-L1 expression, and manageable toxicity in a subset of pts with advanced BTC. Clinical trial information: NCT02054806 and NCT02628067.

3002 Background: CEA CD3 TCB (RG7802, RO6958688) is a novel T-cell bispecific antibody targeting CEA on tumor cells and CD3 on T cells. In preclinical models, CEA CD3 TCB displays potent anti-tumor activity, leads to increased intra-tumoral T cell infiltration and activation and upregulates PD-1/PD-L1. Methods: Intwo ongoing dose-escalation phase I studies, RO6958688 is given as monotherapy (S1) i.v. QW or in combination (QW) with atezolizumab 1200 mg Q3W (S2) in adult patients (pts) with advanced CEA+ solid tumors. In S1, 80 pts (mCRC: 68) were treated at dose levels from 0.05 mg to 600 mg; in S2, 38 pts (mCRC: 28) from 5 mg to 160 mg. In S1, a Bayesian logistic regression model with overdose control guided dose escalation. Data cutoff 25.01.17. Results: At doses ≥60mg (36 pts in S1; 10 in S2), CT scans revealed tumor inflammation within days of first dose, consistent with the mode of action of RO6958688. 2 (5%) pts in S1 (both microsatellite stable (MSS) and 2 (20%; 1 MSS) in S2 had a partial response (RECIST v1.1). Preliminary tumor size reduction ( > -10% and < -30% [stable disease]) was observed in 4 (11%) additional pts in S1 and 5 (50%) in S2. At week 4-6 FDG PET scan assessment, 10 (28%) pts with mCRC in S1 and 6 (60%) in S2 had a metabolic partial response (EORTC criteria). At all doses in S1, the most common related AEs were pyrexia (56.3%), infusion related reaction (IRR, 50%) and diarrhea (40%). The most common grade ≥ 3 (G3) related AEs were IRR (16.3%) and diarrhea (5%). 5 patients experienced DLTs: G3 dyspnea, G3 diarrhea, G3 hypoxia, G4 colitis and G5 respiratory failure (G4-5 at 600mg). DLT events were likely associated with tumor lesion inflammation. In S2, there was no evidence of new or additive toxicities, with 1 DLT at 160 mg (G3 transient increase of ALT in a patient with liver metastases). PK/PD data are reported separately. Conclusions: Evidence of antitumor activity was observed with RO6958688 monotherapy in ongoing dose escalation. Activity appeared to be enhanced with doses in combination with atezolizumab, with a manageable safety profile. Updated data will be presented. Clinical trial information: NCT02324257 and NCT02650713.

Because of the increasing use of biologicals in oncology, many patients are at risk of developing antidrug antibodies (ADAs) during therapy. Although clinical consequences are uncertain, ADAs may affect pharmacokinetics, patient safety, and treatment efficacy. ADA detection and reporting is currently highly inconsistent, which makes it difficult to evaluate the clinical consequences. Standardized reporting of ADA investigations in the context of the aforementioned parameters is critical to understanding the relevance of ADA formation for each drug. Furthermore, the development of trials that specifically aim to investigate clinical prevention strategies in oncology is needed.

Purpose: Stimulation of effector T cells is an appealing immunotherapeutic approach in oncology. OX40 (CD134) is a co-stimulatory receptor expressed on activated CD4+ and CD8+ T cells. Induction of OX40 following antigen recognition results in enhanced T-cell activation, proliferation, and survival, and OX40 targeting shows therapeutic efficacy in preclinical studies. We report the monotherapy dose-escalation portion of a multicenter, phase I trial (NCT02315066) of ivuxolimab (PF-04518600), a fully human immunoglobulin G2 agonistic monoclonal antibody specific for human OX40.Experimental Design: Adult patients (N = 52) with selected locally advanced or metastatic cancers received ivuxolimab 0.01-10 mg/kg. Primary endpoints were safety and tolerability. Secondary/exploratory endpoints included preliminary assessment of antitumor activity, and biomarker analyses. Results:The most common all-causality adverse events were fatigue (46.2%), nausea (28.8%), and decreased appetite (25.0%). Of 31 treatment-related adverse events, 30 (96.8%) were grade ≤2. No dose-limiting toxicities occurred. Ivuxolimab exposure increased in a dose-proportionate manner from 0.3 to 10 mg/kg. Full peripheral blood target engagement occurred at ≥0.3 mg/kg. Three (5.8%) patients achieved a partial response, and disease control was achieved in 56% of patients. Increased CD4+ central memory T-cell proliferation and activation, and clonal expansion of CD4+ and CD8+ T cells in peripheral blood were observed at 0.1 to 3.0 mg/kg. Increased immune cell infiltrate and OX40 expression were evident in on-treatment tumor biopsies.Research.