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Background: First-line durvalumab plus etoposide with either cisplatin or carboplatin (platinum–etoposide) showed a significant improvement in overall survival versus platinum–etoposide alone in patients with extensive-stage small-cell lung cancer (ES-SCLC) in the CASPIAN study. Here we report updated results, including the primary analysis for overall survival with durvalumab plus tremelimumab plus platinum–etoposide versus platinum–etoposide alone. Methods: CASPIAN is an ongoing, open-label, sponsor-blind, randomised, controlled phase 3 trial at 209 cancer treatment centres in 23 countries worldwide. Eligible patients were aged 18 years or older (20 years in Japan) and had treatment-naive, histologically or cytologically documented ES-SCLC, with a WHO performance status of 0 or 1. Patients were randomly assigned (1:1:1) in blocks of six, stratified by planned platinum, using an interactive voice-response or web-response system to receive intravenous durvalumab plus tremelimumab plus platinum–etoposide, durvalumab plus platinum–etoposide, or platinum–etoposide alone. In all groups, patients received etoposide 80–100 mg/m2 on days 1–3 of each cycle with investigator's choice of either carboplatin area under the curve 5–6 mg/mL/min or cisplatin 75–80 mg/m2 on day 1 of each cycle. Patients in the platinum–etoposide group received up to six cycles of platinum–etoposide every 3 weeks and optional prophylactic cranial irradiation (investigator's discretion). Patients in the immunotherapy groups received four cycles of platinum–etoposide plus durvalumab 1500 mg with or without tremelimumab 75 mg every 3 weeks followed by maintenance durvalumab 1500 mg every 4 weeks. The two primary endpoints were overall survival for durvalumab plus platinum–etoposide versus platinum–etoposide and for durvalumab plus tremelimumab plus platinum–etoposide versus platinum–etoposide in the intention-to-treat population. Safety was assessed in all patients who received at least one dose of study treatment. This study is registered at ClinicalTrials.gov, NCT03043872. Findings: Between March 27, 2017, and May 29, 2018, 972 patients were screened and 805 were randomly assigned (268 to durvalumab plus tremelimumab plus platinum–etoposide, 268 to durvalumab plus platinum–etoposide, and 269 to platinum–etoposide). As of Jan 27, 2020, the median follow-up was 25·1 months (IQR 22·3–27·9). Durvalumab plus tremelimumab plus platinum–etoposide was not associated with a significant improvement in overall survival versus platinum–etoposide (hazard ratio [HR] 0·82 [95% CI 0·68–1·00]; p=0·045); median overall survival was 10·4 months (95% CI 9·6–12·0) versus 10·5 months (9·3–11·2). Durvalumab plus platinum–etoposide showed sustained improvement in overall survival versus platinum–etoposide (HR 0·75 [95% CI 0·62–0·91]; nominal p=0·0032); median overall survival was 12·9 months (95% CI 11·3–14·7) versus 10·5 months (9·3–11·2). The most common any-cause grade 3 or worse adverse events were neutropenia (85 [32%] of 266 patients in the durvalumab plus tremelimumab plus platinum–etoposide group, 64 [24%] of 265 patients in the durvalumab plus platinum–etoposide group, and 88 [33%] of 266 patients in the platinum–etoposide group) and anaemia (34 [13%], 24 [9%], and 48 [18%]). Any-cause serious adverse events were reported in 121 (45%) patients in the durvalumab plus tremelimumab plus platinum–etoposide group, 85 (32%) in the durvalumab plus platinum–etoposide group, and 97 (36%) in the platinum–etoposide group. Treatment-related deaths occurred in 12 (5%) patients in the durvalumab plus tremelimumab plus platinum–etoposide group (death, febrile neutropenia, and pulmonary embolism [n=2 each]; enterocolitis, general physical health deterioration and multiple organ dysfunction syndrome, pneumonia, pneumonitis and hepatitis, respiratory failure, and sudden death [n=1 each]), six (2%) patients in the durvalumab plus platinum–etoposide group (cardiac arrest, dehydration, hepatotoxicity, interstitial lung disease, pancytopenia, and sepsis [n=1 each]), and two (1%) in the platinum–etoposide group (pancytopenia and thrombocytopenia [n=1 each]). Interpretation: First-line durvalumab plus platinum–etoposide showed sustained overall survival improvement versus platinum–etoposide but the addition of tremelimumab to durvalumab plus platinum–etoposide did not significantly improve outcomes versus platinum–etoposide. These results support the use of durvalumab plus platinum–etoposide as a new standard of care for the first-line treatment of ES-SCLC. Funding: AstraZeneca.

Background: Most patients with small-cell lung cancer (SCLC) have extensive-stage disease at presentation, and prognosis remains poor. Recently, immunotherapy has demonstrated clinical activity in extensive-stage SCLC (ES-SCLC). The CASPIAN trial assessed durvalumab, with or without tremelimumab, in combination with etoposide plus either cisplatin or carboplatin (platinum–etoposide) in treatment-naive patients with ES-SCLC. Methods: This randomised, open-label, phase 3 trial was done at 209 sites across 23 countries. Eligible patients were adults with untreated ES-SCLC, with WHO performance status 0 or 1 and measurable disease as per Response Evaluation Criteria in Solid Tumors, version 1.1. Patients were randomly assigned (in a 1:1:1 ratio) to durvalumab plus platinum–etoposide; durvalumab plus tremelimumab plus platinum–etoposide; or platinum–etoposide alone. All drugs were administered intravenously. Platinum–etoposide consisted of etoposide 80–100 mg/m2 on days 1–3 of each cycle with investigator's choice of either carboplatin area under the curve 5–6 mg/mL per min or cisplatin 75–80 mg/m2 (administered on day 1 of each cycle). Patients received up to four cycles of platinum–etoposide plus durvalumab 1500 mg with or without tremelimumab 75 mg every 3 weeks followed by maintenance durvalumab 1500 mg every 4 weeks in the immunotherapy groups and up to six cycles of platinum–etoposide every 3 weeks plus prophylactic cranial irradiation (investigator's discretion) in the platinum–etoposide group. The primary endpoint was overall survival in the intention-to-treat population. We report results for the durvalumab plus platinum–etoposide group versus the platinum–etoposide group from a planned interim analysis. Safety was assessed in all patients who received at least one dose of their assigned study treatment. This study is registered at ClinicalTrials.gov, NCT03043872, and is ongoing. Findings: Patients were enrolled between March 27, 2017, and May 29, 2018. 268 patients were allocated to the durvalumab plus platinum–etoposide group and 269 to the platinum–etoposide group. Durvalumab plus platinum–etoposide was associated with a significant improvement in overall survival, with a hazard ratio of 0·73 (95% CI 0·59–0·91; p=0·0047]); median overall survival was 13·0 months (95% CI 11·5–14·8) in the durvalumab plus platinum–etoposide group versus 10·3 months (9·3–11·2) in the platinum–etoposide group, with 34% (26·9–41·0) versus 25% (18·4–31·6) of patients alive at 18 months. Any-cause adverse events of grade 3 or 4 occurred in 163 (62%) of 265 treated patients in the durvalumab plus platinum–etoposide group and 166 (62%) of 266 in the platinum–etoposide group; adverse events leading to death occurred in 13 (5%) and 15 (6%) patients. Interpretation: First-line durvalumab plus platinum–etoposide significantly improved overall survival in patients with ES-SCLC versus a clinically relevant control group. Safety findings were consistent with the known safety profiles of all drugs received. Funding: AstraZeneca.

9041 Background: A Randomized, Double-blind, Phase III Study was conducted to confirm clinical similarity between BAT1706, a proposed biosimilar to reference bevacizumab, and EU-bevacizumab in patients with advanced non-squamous non-small cell lung cancer (NSCLC). Methods: Patients were randomized 1:1 to BAT1706 plus paclitaxel and carboplatin (Arm A) or EU-bevacizumab plus paclitaxel and carboplatin (Arm B) given three weeks for 6 cycles, followed by maintenance therapy with BAT1706 or EU- bevacizumab. The primary endpoint was overall response rate at Week 18 (ORR18). Secondary endpoints included ORR at Week 6 and 12, best ORR, duration of response (DoR), progression-free survival (PFS), and overall survival (OS). Results: A total of 651 patients were randomized: BAT1706 (n = 325) or EU- bevacizumab (n = 326). In total, 649 randomized patients (BAT1706 (n = 325) or EU- bevacizumab (n = 324)) received at least one cycle of combination treatment. The median duration of therapy was 29.1 weeks (ranging from 3.0 to 62.1 weeks) in the Arm A and 27.0 weeks (ranging from 3.0 to 53.9 weeks) in the Arm B. The extent of exposure to BAT1706 and EU- bevacizumab was similar between these two arms. Overall, the proportion of patients achieving an ORR by Week 18 was comparable across Arm A and B (48.0% and 44.5%). The ORR risk ratio of 1.08 with 90% CI (0.94, 1.24) and the ORR risk difference of 0.03, with 95% CI (-0.04, 0.11) were within pre-specified equivalence margin. In addition, the multivariate-adjusted risk ratio was 1.07, with a 90% CI (0.93, 1.22). The ORR18 risk difference between BAT1706 and EU- bevacizumab was 0.03, with the 2-sided 95% CI (-0.04, 0.11) that fell entirely within pre-specified equivalence margin. In addition, the multivariate-adjusted risk difference was 0.03, with a 95% CI (-0.04, 0.11). The hazard ratio stratified for time to PFS was 0.915 and the PFS rate at 12 months was 20.7% versus 21.8%. At the end of the study, there were no significant differences between both the treatments. The incidence of treatment-emergent adverse events (TEAEs) and study drug-related TEAEs was similar between these two arms. Overall, the safety profiles of BAT1706 were consistent with that of EU- bevacizumab, no new safety signals or noticeable trends were observed. The mean serum concentrations were comparable between BAT1706 and EU- bevacizumab over the entire sampling interval both in pre-dose and post-dose. The incidence of positive anti-drug antibodies results was low (≤5%) and decreased over time in both treatment arms. No patient was detected to have positive neutralizing anti-drug antibody result during the study. Conclusions: BAT1706 demonstrated clinical equivalence to reference EU-bevacizumab in terms of efficacy, safety, pharmacokinetics, and immunogenicity. Clinical trial information: NCT03329911.

Human epidermal growth factor receptor 2 (HER2, also known as ERBB2) amplification or overexpression occurs in approximately 20% of advanced gastric or gastro-oesophageal junction adenocarcinomas

4013 Background: Trastuzumab (tras) plus chemotherapy (chemo) is standard-of-care (SOC) 1L therapy for HER2+ metastatic G/GEJ cancer. In two phase 2 studies, tras, chemo, and pembrolizumab (pembro) in combination showed promising efficacy and manageable safety. The ongoing global, randomized, double-blind, placebo-controlled phase 3 KEYNOTE-811 study is assessing whether adding pembro to SOC improves efficacy vs SOC alone for HER2+ metastatic G/GEJ cancer (NCT03615326). Methods: Eligible patients (pts) with previously untreated, unresectable or metastatic HER2+ G/GEJ cancer and ECOG PS 0 or 1 are randomized 1:1 to pembro 200 mg IV Q3W or placebo IV Q3W. All pts receive tras and investigator’s choice of 5-fluorouracil and cisplatin (FP) or capecitabine and oxaliplatin (CAPOX). Treatment is given up to 2 y or until intolerable toxicity or PD. Dual primary end points are PFS per RECIST v1.1 by blinded, independent central review (BICR) and OS. Secondary end points are ORR and DOR per RECIST v1.1 by BICR and safety. Planned enrollment in the global cohort is 692 pts; accrual is almost complete. The protocol-specified first interim analysis (IA1) was to occur when the first 260 pts enrolled had ≥8.5 mo of follow-up and tested whether pembro + SOC significantly improved ORR; the superiority boundary was P = 0.002. The ORR difference was calculated using the Miettinen and Nurminen method stratified by the randomization stratification factors of geographic region, PD-L1 status, and chemo choice. Efficacy is presented for the first 264 pts enrolled. Safety is presented for all treated pts enrolled as of Jun 17, 2020. Results: Among the first 264 pts enrolled, 133 were randomized to pembro + SOC, 131 to placebo + SOC; 0.8% had MSI-H tumors, CAPOX was chosen for 87.1%, and median study follow-up was 12.0 mo (range, 8.5-19.4). Confirmed ORR (95% CI) was 74.4% (66.2-81.6) for pembro + SOC vs 51.9% (43.0-60.7) for placebo + SOC (difference, 22.7 percentage points [95% CI, 11.2-33.7], P = 0.00006); CR rate was 11.3% vs 3.1% and DCR (95% CI) was 96.2% (91.4-98.8) vs 89.3 (82.7-94.0). Median (range) DOR was 10.6 mo (1.1+ to 16.5+) for pembro + SOC vs 9.5 mo (1.4+ to 15.4+) for placebo + SOC; KM estimates of DOR ≥6 mo and ≥9 mo were 70.3% vs 61.4% and 58.4% vs 51.1%. As of data cutoff, 433/434 enrolled pts were treated (217/217 pembro + SOC, 216/217 placebo + SOC). AEs were grade 3-5 in 57.1% of pts with pembro + SOC vs 57.4% with placebo + SOC, led to death in 3.2% vs 4.6%, and led to discontinuation of any drug in 24.4% vs 25.9%. Conclusions: Adding pembro to tras and chemo resulted in a substantial, statistically significant increase in ORR versus trastuzumab and chemo alone as 1L therapy for HER2+ metastatic G/GEJ cancer; responses were durable and safety was manageable. These initial data support pembro plus tras and chemo as a potential new treatment option for this population. Clinical trial information: NCT03615326.

e21542 Background: MB02 is a proposed biosimilar of the reference bevacizumab. A multinational, double-blind, randomized, parallel group clinical study (STELLA) is undergoing to confirm clinical similarity between MB02 and bevacizumab in patients with stage IIIB/IV no squamous NSCLC. Methods: Subjects were randomized 1:1 to MB02 or bevacizumab (15 mg/kg) plus chemotherapy (paclitaxel [P] 200 mg/m2 and carboplatin [C] AUC6) on Day 1 of every 3-week cycle for 6 cycles (Week 18) followed by MB02/bevacizumab in blinded monotherapy until disease progression, treatment intolerance, death, patient withdrawal or end of study (Week 52). As primary study endpoint, the efficacy by means of the objective response rate (ORR) evaluated by an independent radiological committee (IRC) was compared between arms at Week 18. Secondary endpoints were Progression Free Survival (PFS) and Overall Survival (OS), safety and immunogenicity (assessed at 18 and 52 weeks). Results: 627 patients were randomized: MB02 (n = 315) and bevacizumab (n = 312). Demographic and baseline characteristics were well balanced between arms. The ORR results were comparable for subjects receiving MB02 or bevacizumab plus P/C. A Risk Ratio (RR) of 1.013 (90% CI: -0.037% to 0.059) and a Risk Difference (RD) of 0.011 (90% CI: -0.037% to 0.059), were within the similarity margin predefined by FDA (0.73, 1.36) and EMA (-12%, +12%) respectively. This ORR assessed by IRC was consistent with the investigator assessment criteria. There was no significant difference between arms for secondary efficacy endpoints (PFS/OS) at week 18. Up to primary endpoint cut-off point, the safety assessment showed no significant differences between MB02 and bevacizumab arms (including the immunogenicity assessment) in terms of nature, frequency and severity of the adverse events (AE), being anaemia and hypertension the most common IMP-related AEs, with a RD between treatment groups < 5%. New signals or observable trends were no reported for MB02-treated subjects. Additional information on the secondary endpoints will be available at week 52 (end of monotherapy period). Conclusions: The statistical analysis executed for ORRs confirm the equivalence of MB02 and bevacizumab, supporting the clinical activity of MB02 treatment. MB02 was well tolerated with manageable AEs in patients with Stage IIIB/IV NSCLC. Clinical trial information: NCT03296163.