Symbiotic-Lung-04: 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

August 14, 2026 updated by: Pfizer

A GLOBAL PHASE 2/3 INTERVENTIONAL STUDY OF PF-08634404 IN COMBINATION WITH CHEMOTHERAPY IN PARTICIPANTS WITH EXTENSIVE STAGE SMALL CELL LUNG CANCER

This study is being done to learn more about a new medicine called PF-08634404 and how well it works when given with chemotherapy to adults with extensive-stage small cell lung cancer (ES-SCLC), a fast-growing type of lung cancer that has spread widely in the body.

To join the study, participants must meet the following conditions:

  • Be 18 years or older.
  • Have extensive-stage small cell lung cancer confirmed by lab tests.
  • Have not received chemotherapy or radiation for this type of lung cancer.
  • Be in good physical condition and have healthy organs based on medical tests.

The study has two parts:

  • In the first part, researchers will check how safe the study medicine is and how well people tolerate it when given with chemotherapy.
  • In the second part, they will compare study medicine plus chemotherapy to another approved treatment (atezolizumab plus chemotherapy) to see which works better.

Participants will receive the treatment through IV infusions (medicine given directly into a vein). The treatment will be given in repeated time periods called cycles. Some participants will continue receiving the study medicine alone after the initial treatment.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

550

Phase

  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Australia
    • New South Wales
      • Westmead, New South Wales, Australia, 2145
        • Recruiting
        • Westmead Hospital
    • Queensland
      • Birtinya, Queensland, Australia, 4575
        • Recruiting
        • Sunshine Coast University Hospital
  • China
    • Guangdong
      • Guangzhou, Guangdong, China, 510180
        • Recruiting
        • Guangdong Provincial People's Hospital
    • Shanghai Municipality
      • Shanghai, Shanghai Municipality, China, 200032
        • Recruiting
        • Fudan University Shanghai Cancer Center
  • France
      • Villejuif, France, 94805
        • Recruiting
        • Gustave Roussy
    • Île-de-France Region
      • Boulogne-Billancourt, Île-de-France Region, France, 92100
        • Recruiting
        • Hôpital Ambroise Paré
  • Germany
      • Düsseldorf, Germany, 40479
        • Recruiting
        • Marien Hospital Dusseldorf
      • Frankfurt am Main, Germany, 60488
        • Recruiting
        • Krankenhaus Nordwest GmbH
  • Italy
    • Pordenone
      • Aviano, Pordenone, Italy, 33081
        • Recruiting
        • Centro di Riferimento Oncologico (CRO) IRCCS
    • ROME
      • Roma, ROME, Italy, 00144
        • Recruiting
        • IRCCS Istituto Nazionale dei Tumori Regina Elena
    • Turin
      • Orbassano, Turin, Italy, 10043
        • Recruiting
        • Azienda Ospedaliero-Universitaria San Luigi Gonzaga
  • Japan
    • Osaka
      • Hirakata, Osaka, Japan, 573-1191
        • Recruiting
        • Kansai Medical University Hospital
    • Shizuoka
      • Nagaizumi-cho, Shizuoka, Japan, 411-8777
        • Recruiting
        • Shizuoka Cancer Center
    • Tokyo
      • Kotoku, Tokyo, Japan, 135-8550
        • Recruiting
        • Japanese Foundation for Cancer Research
  • Puerto Rico
      • Manati, Puerto Rico, 00674
        • Recruiting
        • Doctor's Center Hematology & Oncology Group
      • Mayagüez, Puerto Rico, 00680
        • Recruiting
        • Pan American Center for Oncology Trials, LLC - Mayaguez Office Mayaguez Medical Center
      • San Juan, Puerto Rico, 00935
        • Recruiting
        • Hospital Oncologico Dr. Isaac Gonzalez-Martinez
      • San Juan, Puerto Rico, 00909
        • Recruiting
        • Pan American Center for Oncology Trials LLC
  • Spain
      • Barcelona, Spain, 08035
        • Recruiting
        • Hospital Universitari Vall d'Hebron
      • Barcelona, Spain, 08003
        • Recruiting
        • Parc de Salut Mar - Hospital del Mar
      • Barcelona, Spain, 08029
        • Recruiting
        • CETIR
      • Jaén, Spain, 23007
        • Recruiting
        • Hospital Universitario de Jaén
    • Andalusia
      • Jaén, Andalusia, Spain, 23007
        • Recruiting
        • HT Médica Jaen LAs Nieves
    • Cádiz
      • Jerez de la Frontera, Cádiz, Spain, 11407
        • Recruiting
        • Hospital Jerez de la Frontera
    • Madrid, Comunidad de
      • Madrid, Madrid, Comunidad de, Spain, 28041
        • Recruiting
        • Hospital Universitario 12 de Octubre
  • Taiwan
      • Tainan, Taiwan, 704302
        • Recruiting
        • National Cheng Kung University Hospital
      • Taipei, Taiwan, 10002
        • Recruiting
        • National Taiwan University Hospital
      • Taipei, Taiwan, 110
        • Recruiting
        • Taipei Medical University Hospital
  • United States
    • Arkansas
      • Fayetteville, Arkansas, United States, 72703
        • Recruiting
        • Highlands Oncology Group
      • Rogers, Arkansas, United States, 72758
        • Recruiting
        • Highlands Oncology Group
      • Springdale, Arkansas, United States, 72762
        • Recruiting
        • Highlands Oncology Group
    • Florida
      • Coral Springs, Florida, United States, 33065
        • Recruiting
        • Brcr Coral Springs
      • Orange City, Florida, United States, 32763
        • Recruiting
        • Mid Florida Hematology and Oncology Center
      • Tamarac, Florida, United States, 33321
        • Recruiting
        • BRCR Global - Tamarac
    • Ohio
      • Cleveland, Ohio, United States, 44106
        • Not yet recruiting
        • University Hospitals Cleveland Medical Center
    • Texas
      • Allen, Texas, United States, 75013
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Arlington, Texas, United States, 76012
        • Not yet recruiting
        • Texas Oncology - DFW
      • Arlington, Texas, United States, 76014
        • Not yet recruiting
        • Texas Oncology - DFW
      • Beaumont, Texas, United States, 77702
        • Recruiting
        • Texas Oncology - Gulf Coast
      • Bedford, Texas, United States, 76022
        • Not yet recruiting
        • Texas Oncology - DFW
      • Dallas, Texas, United States, 75203
        • Not yet recruiting
        • Texas Oncology - DFW
      • Dallas, Texas, United States, 75230
        • Not yet recruiting
        • Texas Oncology - DFW
      • Dallas, Texas, United States, 75231
        • Not yet recruiting
        • Texas Oncology - DFW
      • Dallas, Texas, United States, 75237
        • Not yet recruiting
        • Texas Oncology - DFW
      • Dallas, Texas, United States, 75246
        • Not yet recruiting
        • Texas Oncology - DFW
      • Denison, Texas, United States, 75020
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Denton, Texas, United States, 76201
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Flower Mound, Texas, United States, 75028
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Fort Worth, Texas, United States, 76104
        • Not yet recruiting
        • Texas Oncology - DFW
      • Fredericksburg, Texas, United States, 78624
        • Recruiting
        • Texas Oncology - San Antonio
      • Grapevine, Texas, United States, 76051
        • Not yet recruiting
        • Texas Oncology - DFW
      • Houston, Texas, United States, 77024
        • Recruiting
        • Texas Oncology - Gulf Coast
      • Houston, Texas, United States, 77054
        • Recruiting
        • Texas Oncology - Gulf Coast
      • Irving, Texas, United States, 75063
        • Recruiting
        • US Oncology Investigational Products Center (IPC)
      • Irving, Texas, United States, 75063
        • Not yet recruiting
        • US Oncology Investigational Products Center (IPC)
      • Irving, Texas, United States, 75063
        • Recruiting
        • US Oncology Investigational Product Center (IPC)
      • Lewisville, Texas, United States, 75056
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Longview, Texas, United States, 75601
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • McKinney, Texas, United States, 75071
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • New Braunfels, Texas, United States, 78130
        • Recruiting
        • Texas Oncology - San Antonio
      • Palestine, Texas, United States, 75801
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Paris, Texas, United States, 75460
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Pearland, Texas, United States, 77584
        • Recruiting
        • Texas Oncology - Gulf Coast
      • Plano, Texas, United States, 75075
        • Not yet recruiting
        • Texas Oncology - DFW
      • Plano, Texas, United States, 75093
        • Not yet recruiting
        • Texas Oncology - DFW
      • San Antonio, Texas, United States, 78240
        • Recruiting
        • Texas Oncology - San Antonio
      • San Antonio, Texas, United States, 78217
        • Recruiting
        • Texas Oncology - San Antonio
      • San Antonio, Texas, United States, 78258
        • Recruiting
        • Texas Oncology - San Antonio
      • Sugar Land, Texas, United States, 77479
        • Recruiting
        • Texas Oncology - Gulf Coast
      • The Woodlands, Texas, United States, 77380
        • Recruiting
        • Texas Oncology - Gulf Coast
      • Tyler, Texas, United States, 75702
        • Not yet recruiting
        • Texas Oncology - Northeast Texas
      • Webster, Texas, United States, 77598
        • Recruiting
        • Texas Oncology - Gulf Coast
    • Virginia
      • Blacksburg, Virginia, United States, 24060
        • Recruiting
        • Oncology & Hematology Associates of Southwest Virginia, Inc., DBA Blue Ridge Cancer Care
      • Chesapeake, Virginia, United States, 23320
        • Recruiting
        • Virginia Oncology Associates
      • Hampton, Virginia, United States, 23666
        • Recruiting
        • Virginia Oncology Associates
      • Low Moor, Virginia, United States, 24457
        • Recruiting
        • Oncology & Hematology Associates of Southwest Virginia, Inc., DBA Blue Ridge Cancer Care
      • Newport News, Virginia, United States, 23606
        • Recruiting
        • Virginia Oncology Associates
      • Norfolk, Virginia, United States, 23502
        • Recruiting
        • Virginia Oncology Associates
      • Roanoke, Virginia, United States, 24014
        • Recruiting
        • Oncology & Hematology Associates of Southwest Virginia, Inc., DBA Blue Ridge Cancer Care
      • Salem, Virginia, United States, 24153
        • Recruiting
        • Oncology & Hematology Associates of Southwest Virginia, Inc., DBA Blue Ridge Cancer Care
      • Virginia Beach, Virginia, United States, 23456
        • Recruiting
        • Virginia Oncology Associates
      • Williamsburg, Virginia, United States, 23188
        • Recruiting
        • Virginia Oncology Associates
      • Wytheville, Virginia, United States, 24382
        • Recruiting
        • Oncology & Hematology Associates of Southwest Virginia, Inc., DBA Blue Ridge Cancer Care

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Phase 2 Single arm
Participants will receive PF-08634404 in combination with chemotherapy
Drug: Chemotherapy
Injection for intravenous use
Drug: PF-08634404
Concentrate for solution for infusion
Experimental: Phase 3 Experimental Arm
Participants will receive PF-08634404 in combination with chemotherapy
Drug: Chemotherapy
Injection for intravenous use
Drug: PF-08634404
Concentrate for solution for infusion
Active Comparator: Phase3 Control Arm
Participants will receive atezolizumab in combination with chemotherapy
Drug: Chemotherapy
Injection for intravenous use
Biological: Atezolizumab
Injection for intravenous use

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to 90 days after the last dose of treatment
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.
Up to approximately 2 years after completion of study treatment of last study participant

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to 90 days after the last dose of treatment
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.
Up to 90 days after the last dose of treatment
Pharmacokinetics: Serum concentrations of PF-08634404
Time Frame: Up to 37 days after the last dose of treatment
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
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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.
Up to approximately 2 years after completion of study treatment of last study participant
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 progressive disease (PD) or death due to any cause.
Up to approximately 2 years after completion of study treatment of last study participant
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 PD assessed by BICR per RECIST v1.1, or death due to any cause, whichever occurs first.
Up to approximately 2 years after completion of study treatment of last study participant

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Pfizer

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 9, 2025

Primary Completion (Estimated)

June 14, 2030

Study Completion (Estimated)

March 11, 2034

Study Registration Dates

First Submitted

November 7, 2025

First Submitted That Met QC Criteria

November 7, 2025

First Posted (Actual)

November 12, 2025

Study Record Updates

Last Update Posted (Actual)

August 17, 2026

Last Update Submitted That Met QC Criteria

August 14, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • C6461004
  • 2025-523522-41-00 (Ctis)
  • Symbiotic-Lung-04 (Other Identifier: Pfizer)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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