A GLOBAL PHASE 2/3 INTERVENTIONAL STUDY OF PF-08634404 IN COMBINATION WITH CHEMOTHERAPY IN PARTICIPANTS WITH EXTENSIVE STAGE SMALL CELL LUNG CANCER
A Study to Learn About the Study Medicine Called PF-08634404 in Combination With Chemotherapy in Adult Participants With Extensive-Stage Small Cell Lung Cancer
Kawai Norisuke
Pfizer R&D Japan G.K.
Shinjuku Bunka Quint Bldg., 3-22-7 Yoyogi, Shibuya-ku, Tokyo
+81-3-5309-7000
clinical-trials@pfizer.com
Clinical Trials Information Desk
Pfizer R&D Japan G.K.
Shinjuku Bunka Quint Bldg., 3-22-7 Yoyogi, Shibuya-ku, Tokyo
+81-3-5309-7000
clinical-trials@pfizer.com
Recruiting
Feb. 17, 2026
Feb. 17, 2026
550
Interventional
randomized controlled trial
double blind
active control
parallel assignment
treatment purpose
Inclusion Criteria:
*Histologically or cytologically confirmed extensive-stage small cell lung cancer (ES-SCLC).
*Participants have not received systemic therapy (chemotherapy, radiotherapy, chemoradiation) for ES-SCLC.
*Treatment-free for at least 6 months since last chemo/radiotherapy, among those treated (with curative intent) with prior chemo/radiotherapy for limited-stage SCLC
*Have at least one measurable lesion as the targeted lesion based on RECIST V1.1.
*Eastern Cooperative Oncology Group performance status of 0 or 1.
*Adequate organ function
Exclusion Criteria:
*known active CNS lesions, including brainstem, meningeal, or spinal cord metastases or compression
*Leptomeningeal disease
*Clinically significant risk of hemorrhage or fistula
*history of another malignancy within 3 years
*active autoimmune diseases requiring systemic treatment within the past 2 years
18age old over
No limit
Both
Small Cell Lung Cancer (SCLC)
*Drug: PF-08634404
-Concentrate for solution for infusion
*Biological: Atezolizumab
-Injection for intravenous use
*Drug: Chemotherapy
-Injection for intravenous use
*Phase 2: Confirmed Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST 1.1] based on the investigator's assessment [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-Defined as the proportion of participants in whom a confirmed complete response (CR) or partial response (PR) is observed as best overall response. ORR using RECIST v1.1 as assessed by investigator.
*Phase 2: Number of participants with treatment-emergent adverse events [Time Frame: Up to 90 days after the last dose of treatment]
-Adverse Events (AEs) as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), timing, seriousness, and relationship to study intervention.
*Phase 3: Overall Survival (OS) [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-OS is defined as the time from the date of randomization to the date of death due to any cause. OS is secondary outcome measure in Phase 2 portion of the study.
*Duration of Response (DOR) as assessed by Investigator based on RECIST v1.1 [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-DOR is defined as the time from the first documentation of objective response (CR or PR) to the date of first documentation of PD or death due to any cause.
*Progression Free Survival (PFS) as assessed by investigator based on RECIST v1.1 [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-PFS is defined as the time from the date of randomization to the date of first documented disease progression, per RECIST v1.1, or death to any cause, whichever occurs first
*Number of participants with Laboratory abnormalities [Time Frame: Up to 90 days after the last dose of treatment]
-Laboratory abnormalities as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), and timing.
*Phase 2: Number of Participants who Experience a Dose-Limiting Toxicity (DLT) [Time Frame: Up to 90 days after the last dose of treatment]
-DLT (any of the prespecified AEs that are attributable to study treatment(s), excluding toxicities clearly due to underlying disease or extraneous causes) rate estimated based on data from DLT-evaluable participants during the DLT evaluation period.
*Pharmacokinetics: Serum concentrations of PF-08634404 [Time Frame: Up to 37 days after the last dose of treatment]
*Incidence of antidrug antibody against PF-08634404 [Time Frame: Up to 37 days after the last dose of treatment]
*Phase 2: Overall Survival [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-Overall survival defined as the time from the date of randomization to the date of death due to any cause.
*Phase 3: PFS using RECIST v1.1 as assessed by blinded independent central review (BICR) [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-Progression Free Survival (PFS) is defined as the time from the date of randomization to the date of the first documentation of objective progressive disease (PD) assessed by BICR per RECIST v1.1, or death due to any cause, whichever occurs first.
*Phase 3: Confirmed ORR using RECIST v1.1 as assessed by BICR [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-ORR is defined as the proportion of participants in the analysis population having a best overall response (BOR) of confirmed CR or confirmed PR according to RECIST v1.1 as assessed by BICR.
*Phase 3: DOR using RECIST v1.1 as assessed by BICR [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-The time from the first documentation of objective response (CR or PR that is subsequently confirmed) to the date of the first documentation of PD as determined by BICR assessment per RECIST v1.1, or death due to any cause, whichever occurs first.
*Phase 3: Mean scores and Change from baseline in the global health status/quality of life (QoL), function, and symptom scores on the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-The EORTC QLQ-C30 is a questionnaire for quantitative measure of health-related quality of life pertinent to participants with a broad range of cancers who are participating in international clinical trials.
*Phase 3: Mean scores and Change from Baseline on the EORTC Quality of Life Cancer Questionnaire - Lung Cancer 13 (EORTC QLQ-LC13) [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-EORTC QLQ-LC13 is a lung cancer specific module that serves as an additional 13 item questionnaire to the general EORTC cancer questionnaire, the EORTC QLQ-C30.
*Phase 3: Time to definitive deterioration (TTdD) in the global health status/QoL, function, and symptom scores on the EORTC QLQ-C30 [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-TTdD is defined as the time from date of randomization to first onset of Patient Reported Outcome (PRO) deterioration without subsequent recovery.
*Phase 3: TTdD in the dyspnea, cough, and chest pain scores on the EORTC QLQ-LC13 [Time Frame: Up to approximately 2 years after completion of study treatment of last study participant]
-TTdD is defined as the time from date of randomization to first onset of Patient Reported Outcome (PRO) deterioration without subsequent recovery.
Pfizer Japan Inc.
Review Board of Human Rights and Ethics for Clinical Studies Institutional Review Board
2-2-1, Kyobashi, Chuo-ku, Tokyo
+81-3-6665-0572
soudan@hurecs.org
Approval
Dec. 10, 2025
Yes
Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
