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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.

This article reviews the role of ALK tyrosine kinase inhibitors (TKIs) in the literature and provides expert commentary on local use in Argentina, Brazil, China, Russia, South Korea, and Turkey. We identified 56 articles involving patients with ALK-positive non-small cell lung cancer (NSCLC) and brain metastases (BM) treated with ALK TKIs published between January 2000 and June 2021. In first-line settings, central nervous system response rates in clinical trials with alectinib (86-94%), brigatinib (67-78%), and lorlatinib (42-82%) were generally higher than those reported with crizotinib (16-71%). Median progression-free survival in patients receiving crizotinib (5.6-7.4 months) was lower than alectinib (not reached), brigatinib (24.0 months), and ceritinib (10.7-25.2 months). Across these counties, next-generation TKIs are preferred for patients with progressing BM lesions. Although next-generation ALK TKIs demonstrate significant activity in these patients and following progression on crizotinib, access remains a challenge for personalized therapy.

In the phase 1/3 IMpower133 study, atezolizumab plus carboplatin and etoposide (CP/ET) followed by maintenance atezolizumab for first-line treatment of extensive-stage SCLC (ES-SCLC) led to improvement in both overall survival (OS) and progression-free survival (PFS) versus placebo plus CP/ET followed by maintenance placebo. We explored the benefit of atezolizumab versus placebo in the subset of patients who reached the IMpower133 maintenance phase and the safety profile of maintenance therapy.Patients with untreated ES-SCLC were randomized 1:1 to four 21-day cycles of CP/ET with atezolizumab or placebo, followed by maintenance atezolizumab or placebo. The primary end points were OS and investigator-assessed PFS. A multivariate Cox model from the start of maintenance treatment was used to evaluate the treatment effect and account for lead-time bias; a generalized linear model was used to identify prognostic or predictive characteristics for reaching the maintenance phase.A similar proportion of patients in each arm received at least the first dose of maintenance therapy (atezolizumab: 77%, n = 154 of 201; placebo: 81%, n = 164 of 202) and were included in the maintenance analysis population. An Eastern Cooperative Oncology Group performance status of 0 and absence of liver metastases at baseline were identified as prognostic factors for reaching the maintenance phase. The positive treatment effect with atezolizumab remained after adjusting for baseline characteristics. Median OS and PFS from the start of maintenance therapy in the atezolizumab versus placebo arm were 12.5 versus 8.4 months (hazard ratio = 0.59, 95% confidence interval: 0.43-0.80) and 2.6 versus 1.8 months (hazard ratio = 0.63 [95% confidence interval: 0.49-0.80]), respectively. Treatment-related adverse events from the start of maintenance therapy occurred in 41% (n = 64 of 155) and 25% (n = 41 of 163) of safety-evaluable patients in the atezolizumab and placebo arms, respectively, and were grade 3 or 4 in 28% (n = 43 of 155) and 23% (n = 37 of 163) of the respective populations; no patient in the atezolizumab arm and one patient in the placebo arm had a grade 5 treatment-related adverse event.These data in the context of other immunotherapy trials in ES-SCLC suggest that induction with atezolizumab plus CP/ET and maintenance treatment with atezolizumab are important components that contributed to the OS benefit observed in IMpower133. Safety results from randomization and from the start of maintenance therapy were similar between the treatment arms despite the continuation of atezolizumab in the maintenance phase.

BACKGROUND: Pembrolizumab is active in head and neck squamous cell carcinoma (HNSCC), with programmed cell death ligand 1 (PD-L1) expression associated with improved response.METHODS: KEYNOTE-048 was a randomised, phase 3 study of participants with untreated locally incurable recurrent or metastatic HNSCC done at 200 sites in 37 countries. Participants were stratified by PD-L1 expression, p16 status, and performance status and randomly allocated (1:1:1) to pembrolizumab alone, pembrolizumab plus a platinum and 5-fluorouracil (pembrolizumab with chemotherapy), or cetuximab plus a platinum and 5-fluorouracil (cetuximab with chemotherapy). Investigators and participants were aware of treatment assignment. Investigators, participants, and representatives of the sponsor were masked to the PD-L1 combined positive score (CPS) results; PD-L1 positivity was not required for study entry. The primary endpoints were overall survival (time from randomisation to death from any cause) and progression-free survival (time from randomisation to radiographically confirmed disease progression or death from any cause, whichever came first) in the intention-to-treat population (all participants randomly allocated to a treatment group). There were 14 primary hypotheses: superiority of pembrolizumab alone and of pembrolizumab with chemotherapy versus cetuximab with chemotherapy for overall survival and progression-free survival in the PD-L1 CPS of 20 or more, CPS of 1 or more, and total populations and non-inferiority (non-inferiority margin: 1·2) of pembrolizumab alone and pembrolizumab with chemotherapy versus cetuximab with chemotherapy for overall survival in the total population. The definitive findings for each hypothesis were obtained when statistical testing was completed for that hypothesis; this occurred at the second interim analysis for 11 hypotheses and at final analysis for three hypotheses. Safety was assessed in the as-treated population (all participants who received at least one dose of allocated treatment). This study is registered at ClinicalTrials.gov, number NCT02358031.FINDINGS: Between April 20, 2015, and Jan 17, 2017, 882 participants were allocated to receive pembrolizumab alone (n=301), pembrolizumab with chemotherapy (n=281), or cetuximab with chemotherapy (n=300); of these, 754 (85%) had CPS of 1 or more and 381 (43%) had CPS of 20 or more. At the second interim analysis, pembrolizumab alone improved overall survival versus cetuximab with chemotherapy in the CPS of 20 or more population (median 14·9 months vs 10·7 months, hazard ratio [HR] 0·61 [95% CI 0·45-0·83], p=0·0007) and CPS of 1 or more population (12·3 vs 10·3, 0·78 [0·64-0·96], p=0·0086) and was non-inferior in the total population (11·6 vs 10·7, 0·85 [0·71-1·03]). Pembrolizumab with chemotherapy improved overall survival versus cetuximab with chemotherapy in the total population (13·0 months vs 10·7 months, HR 0·77 [95% CI 0·63-0·93], p=0·0034) at the second interim analysis and in the CPS of 20 or more population (14·7 vs 11·0, 0·60 [0·45-0·82], p=0·0004) and CPS of 1 or more population (13·6 vs 10·4, 0·65 [0·53-0·80], pINTERPRETATION: Based on the observed efficacy and safety, pembrolizumab plus platinum and 5-fluorouracil is an appropriate first-line treatment for recurrent or metastatic HNSCC and pembrolizumab monotherapy is an appropriate first-line treatment for PD-L1-positive recurrent or metastatic HNSCC.FUNDING: Merck Sharp & Dohme.

TPS8606 Background: Current standard of care immunotherapy plus chemotherapy options for first-line extensive-stage small-cell lung cancer (ES-SCLC) are associated with modest improvements in median OS and PFS. In the KEYNOTE-604 study, first-line pembrolizumab plus etoposide/platinum (EP) significantly improved PFS (HR 0.75; 95% CI, 0.61‒0.91; P = 0.0023) compared with placebo plus EP in ES-SCLC; OS was also longer with pembrolizumab plus EP vs placebo plus EP but did not reach statistical significance (HR 0.80; 95% CI, 0.64‒0.98; P = 0.0164). Preclinical and clinical data suggest that blocking the interaction between the T-cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT) and its ligands CD112 and CD155 with the anti-TIGIT humanized monoclonal antibody vibostolimab (MK-7684) yields promising antitumor activity when combined with pembrolizumab, with or without chemotherapy, including in patients with lung cancer. The current phase 3 study, KeyVibe-008 (NCT05224141), is comparing the efficacy and safety of first-line treatment with MK-7684A, a co-formulation of vibostolimab plus pembrolizumab, in combination with EP vs atezolizumab plus EP in patients with ES-SCLC. Methods: This multicenter, randomized, double-blind, phase 3 study is enrolling patients aged ≥18 years with histologically or cytologically confirmed, previously untreated ES-SCLC. Patients must have measurable disease per RECIST v1.1; ECOG PS of 0 or 1; no active CNS metastases/carcinomatous meningitis, autoimmune disease, neurologic paraneoplastic syndromes, pneumonitis, or interstitial lung disease; and must provide a pretreatment tumor sample. Patients are randomized 1:1 to receive up to 4 cycles of EP (cisplatin or carboplatin) in combination with MK-7684A (vibostolimab 200 mg + pembrolizumab 200 mg) Q3W or atezolizumab (1200 mg) Q3W, followed by MK-7684A or atezolizumab, respectively, until disease progression, unacceptable AEs, intercurrent illness, protocol violation, or investigator/patient decision. Randomization is stratified by ECOG PS (0 vs 1), LDH (≤ULN vs > ULN), liver metastases (yes vs no), and brain metastases (yes vs no). The primary endpoint is OS. Secondary endpoints include PFS, ORR, and duration of response per RECIST v1.1 by blinded independent central review; safety; and patient-reported outcomes (PROs). Tumor imaging occurs at baseline, every 6 weeks until 48 weeks, and every 9 weeks thereafter until disease progression, start of new anticancer treatment, withdrawal of consent, or death. PROs are assessed using validated instruments including the EORTC quality of life and EuroQol questionnaires. AEs are graded according to NCI CTCAE v5.0. Enrollment is ongoing worldwide. Clinical trial information: NCT05224141.

Background: Survival outcomes are poor for patients with metastatic urothelial carcinoma who receive standard, first-line, platinum-based chemotherapy. We assessed the overall survival of patients who received durvalumab (a PD-L1 inhibitor), with or without tremelimumab (a CTLA-4 inhibitor), as a first-line treatment for metastatic urothelial carcinoma.Methods: DANUBE is an open-label, randomised, controlled, phase 3 trial in patients with untreated, unresectable, locally advanced or metastatic urothelial carcinoma, conducted at 224 academic research centres, hospitals, and oncology clinics in 23 countries. Eligible patients were aged 18 years or older with an Eastern Cooperative Oncology Group performance status of 0 or 1. We randomly assigned patients (1:1:1) to receive durvalumab monotherapy (1500 mg) administered intravenously every 4 weeks; durvalumab (1500 mg) plus tremelimumab (75 mg) administered intravenously every 4 weeks for up to four doses, followed by durvalumab maintenance (1500 mg) every 4 weeks; or standard-of-care chemotherapy (gemcitabine plus cisplatin or gemcitabine plus carboplatin, depending on cisplatin eligibility) administered intravenously for up to six cycles. Randomisation was done through an interactive voice–web response system, with stratification by cisplatin eligibility, PD-L1 status, and presence or absence of liver metastases, lung metastases, or both. The coprimary endpoints were overall survival compared between the durvalumab monotherapy versus chemotherapy groups in the population of patients with high PD-L1 expression (the high PD-L1 population) and between the durvalumab plus tremelimumab versus chemotherapy groups in the intention-to-treat population (all randomly assigned patients). The study has completed enrolment and the final analysis of overall survival is reported. The trial is registered with ClinicalTrials.gov, NCT02516241, and the EU Clinical Trials Register, EudraCT number 2015-001633-24.Findings: Between Nov 24, 2015, and March 21, 2017, we randomly assigned 1032 patients to receive durvalumab (n=346), durvalumab plus tremelimumab (n=342), or chemotherapy (n=344). At data cutoff (Jan 27, 2020), median follow-up for survival was 41·2 months (IQR 37·9–43·2) for all patients. In the high PD-L1 population, median overall survival was 14·4 months (95% CI 10·4–17·3) in the durvalumab monotherapy group (n=209) versus 12·1 months (10·4–15·0) in the chemotherapy group (n=207; hazard ratio 0·89, 95% CI 0·71–1·11; p=0·30). In the intention-to-treat population, median overall survival was 15·1 months (13·1–18·0) in the durvalumab plus tremelimumab group versus 12·1 months (10·9–14·0) in the chemotherapy group (0·85, 95% CI 0·72–1·02; p=0·075). In the safety population, grade 3 or 4 treatment-related adverse events occurred in 47 (14%) of 345 patients in the durvalumab group, 93 (27%) of 340 patients in the durvalumab plus tremelimumab group, and in 188 (60%) of 313 patients in the chemotherapy group. The most common grade 3 or 4 treatment-related adverse event was increased lipase in the durvalumab group (seven [2%] of 345 patients) and in the durvalumab plus tremelimumab group (16 [5%] of 340 patients), and neutropenia in the chemotherapy group (66 [21%] of 313 patients). Serious treatment-related adverse events occurred in 30 (9%) of 345 patients in the durvalumab group, 78 (23%) of 340 patients in the durvalumab plus tremelimumab group, and 50 (16%) of 313 patients in the chemotherapy group. Deaths due to study drug toxicity were reported in two (1%) patients in the durvalumab group (acute hepatic failure and hepatitis), two (1%) patients in the durvalumab plus tremelimumab group (septic shock and pneumonitis), and one (Interpretation: This study did not meet either of its coprimary endpoints. Further research to identify the patients with previously untreated metastatic urothelial carcinoma who benefit from treatment with immune checkpoint inhibitors, either alone or in combination regimens, is warranted.Funding: AstraZeneca.

Contains fulltext : 225429.pdf (Publisher’s version ) (Open Access) IMPORTANCE: Checkpoint inhibitors targeting programmed cell death 1 or its ligand (PD-L1) as monotherapies or in combination with anti-cytotoxic T-lymphocyte-associated antigen 4 have shown clinical activity in patients with metastatic non-small cell lung cancer. OBJECTIVE: To compare durvalumab, with or without tremelimumab, with chemotherapy as a first-line treatment for patients with metastatic non-small cell lung cancer. DESIGN, SETTING, AND PARTICIPANTS: This open-label, phase 3 randomized clinical trial (MYSTIC) was conducted at 203 cancer treatment centers in 17 countries. Patients with treatment-naive, metastatic non-small cell lung cancer who had no sensitizing EGFR or ALK genetic alterations were randomized to receive treatment with durvalumab, durvalumab plus tremelimumab, or chemotherapy. Data were collected from July 21, 2015, to October 30, 2018. INTERVENTIONS: Patients were randomized (1:1:1) to receive treatment with durvalumab (20 mg/kg every 4 weeks), durvalumab (20 mg/kg every 4 weeks) plus tremelimumab (1 mg/kg every 4 weeks, up to 4 doses), or platinum-based doublet chemotherapy. MAIN OUTCOMES AND MEASURES: The primary end points, assessed in patients with ≥25% of tumor cells expressing PD-L1, were overall survival (OS) for durvalumab vs chemotherapy, and OS and progression-free survival (PFS) for durvalumab plus tremelimumab vs chemotherapy. Analysis of blood tumor mutational burden (bTMB) was exploratory. RESULTS: Between July 21, 2015, and June 8, 2016, 1118 patients were randomized. Baseline demographic and disease characteristics were balanced between treatment groups. Among 488 patients with ≥25% of tumor cells expressing PD-L1, median OS was 16.3 months (95% CI, 12.2-20.8) with durvalumab vs 12.9 months (95% CI, 10.5-15.0) with chemotherapy (hazard ratio [HR], 0.76; 97.54% CI, 0.56-1.02; P = .04 [nonsignificant]). Median OS was 11.9 months (95% CI, 9.0-17.7) with durvalumab plus tremelimumab (HR vs chemotherapy, 0.85; 98.77% CI, 0.61-1.17; P = .20). Median PFS was 3.9 months (95% CI, 2.8-5.0) with durvalumab plus tremelimumab vs 5.4 months (95% CI, 4.6-5.8) with chemotherapy (HR, 1.05; 99.5% CI, 0.72-1.53; P = .71). Among 809 patients with evaluable bTMB, those with a bTMB ≥20 mutations per megabase showed improved OS for durvalumab plus tremelimumab vs chemotherapy (median OS, 21.9 months [95% CI, 11.4-32.8] vs 10.0 months [95% CI, 8.1-11.7]; HR, 0.49; 95% CI, 0.32-0.74). Treatment-related adverse events of grade 3 or higher occurred in 55 (14.9%) of 369 patients who received treatment with durvalumab, 85 (22.9%) of 371 patients who received treatment with durvalumab plus tremelimumab, and 119 (33.8%) of 352 patients who received treatment with chemotherapy. These adverse events led to death in 2 (0.5%), 6 (1.6%), and 3 (0.9%) patients, respectively. CONCLUSIONS AND RELEVANCE: The phase 3 MYSTIC study did not meet its primary end points of improved OS with durvalumab vs chemotherapy or improved OS or PFS with durvalumab plus tremelimumab vs chemotherapy in patients with ≥25% of tumor cells expressing PD-L1. Exploratory analyses identified a bTMB threshold of ≥20 mutations per megabase for optimal OS benefit with durvalumab plus tremelimumab. TRIAL REGISTRATION: ClinicalT rials.gov Identifier: NCT02453282.

Background High TMB is predictive of PFS benefit with anti-PD-(L)1 ± anti-CTLA-4 therapy in mNSCLC. Preliminary results from MYSTIC (NCT02453282), an open-label, Phase III trial of first-line durvalumab (D; anti-PD-L1), ± tremelimumab (T; anti-CTLA-4), vs platinum-based chemotherapy (CT) in mNSCLC, indicate that blood TMB (bTMB, ≥16 mut/Mb; GuardantOMNI [Guardant Health]) from circulating tumor DNA (ctDNA) correlates positively with tissue (t) TMB (≥10 mut/Mb) (Spearman’s correlation coefficient = 0.6) and is predictive of survival benefit with D±T vs CT. Efficacy outcomes were assessed using additional exploratory cut-offs for bTMB and ≥10 mut/Mb for tTMB. Methods Pts with EGFR and ALK wild-type, immunotherapy/CT-naïve mNSCLC were randomized (1:1:1) to D (20 mg/kg i.v. q4w); D (20 mg/kg i.v. q4w) + T (1 mg/kg i.v. q4w up to 4 doses); or CT. bTMB was evaluated with the GuardantOMNI platform. tTMB was evaluated with the FoundationOne tissue NGS platform. bTMB cut-off was defined as ≥20 mut/Mb (bTMB≥20). Data cut-off: Oct 4, 2018 (OS); Jun 1, 2017 (PFS). Results 1118 pts were randomized. Baseline sample datasets were: bTMB 809; tTMB 460 pts, with baseline characteristics balanced between treatment arms. bTMB≥20 was associated with improved OS (D+T vs CT: HR 0.49 [95% CI 0.32, 0.74]; D vs CT: HR 0.72 [95% CI 0.50, 1.05]) and PFS (D+T vs CT: HR 0.53 [95% CI 0.34, 0.81]; D vs CT: HR 0.77; [95% CI 0.52, 1.13]); 24-mo survival: D+T 48.1% (95% CI 35.5, 59.7), D 33.8% (95% CI 23.4, 44.5) and CT 19.4% (95% CI 11.0, 29.5). Data for tTMB are shown (table). Additional cut-offs will be presented. Conclusion MYSTIC provides the most comprehensive data set to date supporting TMB as a predictive biomarker of OS benefit with immunotherapy. In exploratory analyses, bTMB≥20 was associated with OS and PFS benefit with D±T vs CT, with the greatest magnitude of benefit observed for pts receiving D+T. bTMB ≥20 mut/MbbTMB Citation Format: Solange Peters, Byoung Chul Cho, Niels Reinmuth, Ki Hyeong Lee, Alexander Luft, Myung-Ju Ahn, Paul Baas, Manuel Cobo Dols, Alexey Smolin, David Vicente, Vladimir Moiseyenko, Scott J. Antonia, Kazuhiko Nakagawa, Sarah B. Goldberg, Edward Kim, Rajiv Raja, Philip Brohawn, Delyth Clemett, Piruntha Thiyagarajah, Urban Scheuring, Feng Liu, Naiyer Rizvi. Tumor mutational burden (TMB) as a biomarker of survival in metastatic non-small cell lung cancer (mNSCLC): Blood and tissue TMB analysis from MYSTIC, a Phase III study of first-line durvalumab ± tremelimumab vs chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT074.

9016 Background: MYSTIC, an open-label, Ph3 trial of first-line D (anti-PD-L1) ± T (anti-CTLA-4) vs platinum-based CT, showed an improvement in OS with D vs CT in pts with tumor cell PD-L1 expression ≥25% (PD-L1 TC ≥25%; HR 0.76 [97.54% CI 0.56–1.02], p = 0.036). Exploratory analyses showed bTMB was a predictive biomarker for OS with D±T vs CT. We report further exploratory analyses of OS according to PD-L1 and bTMB. Methods: Immunotherapy/CT-naïve pts with mNSCLC were randomized (1:1:1) to D, D+T or CT. bTMB levels (mut/Mb) were evaluated with the GuardantOMNI platform (Guardant Health), and PD-L1 TC expression with the VENTANA PD-L1 (SP263) IHC assay. Results: D improved OS vs CT in pts with PD-L1 TC ≥25% across bTMB levels (PD-L1 TC ≥25%/bTMB≥20 HR 0.79 [95% CI 0.45, 1.39]; PD-L1 TC ≥25%/bTMB < 20 HR 0.64 [95% CI 0.45, 0.90]). In contrast, D+T improved OS vs CT in pts with bTMB≥20 across different PD-L1 TC expression levels (Table; PD-L1 TC ≥25%/bTMB≥20 HR 0.44 [95% CI 0.23, 0.84]; PD-L1 TC < 1%/bTMB≥20 HR 0.42 [95% CI 0.17, 0.97]). Additional cutoffs and outcomes in subgroups defined by both biomarkers will be presented. Conclusions: These exploratory analyses from MYSTIC support PD-L1 TC expression as an appropriate predictive biomarker for OS with D vs CT, while suggesting bTMB as a predictive biomarker for OS with D+T in mNSCLC. These biomarkers appear to be independent and both may be important for mNSCLC treatment decisions. Interpretation of these data may be limited by small sample sizes; further investigations are warranted. Clinical trial information: NCT02453282. [Table: see text]