Symbiotic-Lung-14: A Study to Learn About the Study Medicine Called PF08634404 in Combination With Chemotherapy in Adult Participants With Transformed Small Cell Lung Cancer

• PF-08634404 (Drug), also known as SSGJ-707: Concentrate for solution for infusion
• Chemotherapy (Drug): Injection for intravenous use

Primary outcomes

• Confirmed Objective Response Rate (ORR) as assessed by investigator based on Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) [From start of treatment until first documented CR or PR (approximately maximum up to 1 years)]: 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.
• Number of Participants with Adverse Events (AEs) [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.

Secondary outcomes

• Duration of Response (DOR) as assessed by investigator based on RECIST v1.1 [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 disease progression (PD) or death due to any cause.
• Progression Free Survival (PFS) as assessed by investigator based on RECIST v1.1 [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
• Overall Survival (OS) [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.
• Number of participants with Laboratory abnormalities [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.
• Pharmacokinetics: Predose and postdose Serum concentrations of PF-08634404 [Up to 37 days after the last dose of treatment]
• Incidence of antidrug antibody against PF-08634404 [Up to 37 days after the last dose of treatment]

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Male or female participants aged ≥18 years at the time of informed consent.
* Histologically or cytologically confirmed T-SCLC. Participant must have had a prior diagnosis of NSCLC with EGFR mutation which transformed to SCLC following the treatment with TKI(s).
* Participants have not received systemic therapy for T-SCLC.
* Have at least one measurable lesion as the target lesion based on RECIST v1.1.
* Have sufficient tumor tissue from the diagnosis of transformed SCLC available.
* Eastern Cooperative Oncology Group performance status of 0 or 1.
* Have a minimum life expectancy of >12 weeks.
* Clinical laboratory values at screening within acceptable limits, as defined in the protocol, including: 1) Hematology, 2) Liver function and 3) Renal function.

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

* Active or untreated CNS disease, including brain, brainstem, spinal cord, or meningeal metastases. Participants with definitively treated, clinically stable brain metastases may be eligible per protocol criteria. Participants with untreated asymptomatic brain metastases of longest diameter <1 cm are permitted if all of the following criteria are met: absence of neurological symptoms, no need for corticosteroids, and brain metastasis has no evidence of edema or hemorrhagic features.
* Leptomeningeal disease
* Clinically significant risk of hemorrhage or fistula, including tumor necrosis/cavitation, invasion or compression of major blood vessels, airways, or critical organs, or risk of tracheoesophageal or pleuroesophageal fistula
* History of another malignancy (other than NSCLC) within 3 years prior to first dose, except for malignancies with negligible risk of metastasis or death (eg, adequately treated carcinoma in situ, nonmelanoma skin cancer)
* Unresolved toxicity from prior anti-tumor therapy that has not recovered to Grade ≤1 per NCI CTCAE v5.0 (except alopecia or irreversible toxicities deemed stable)
* History of allogeneic organ or hematopoietic stem cell transplantation
* Active autoimmune disease requiring systemic treatment within the past 2 years (Stable replacement therapy and selected low-risk autoimmune conditions are permitted per protocol)
* Interstitial lung disease (ILD), pneumonitis, or significant pulmonary disease, including:

  * Prior or current non-infectious pneumonitis requiring systemic therapy
  * DLCO <50% predicted
  * Severe asthma, COPD, pulmonary embolism, or autoimmune lung involvement
* Uncontrolled or clinically significant cardiovascular, cerebrovascular, metabolic, hepatic, or renal disease within 6 months prior to first dose
* Baseline QTcF >480 msec
* Major surgery or severe trauma within 4 weeks prior to first dose, or planned major surgery during the study
* Clinically significant pleural effusion, pericardial effusion, or ascites requiring repeated drainage
* History of significant bleeding disorders or recent major bleeding events
* Clinically significant gastrointestinal conditions, including recent perforation, fistula, obstruction, or active bleeding
* Active, uncontrolled, or symptomatic infection, including:

  * Active TB
  * Active hepatitis B or C
  * Uncontrolled HIV infection
* History of immunodeficiency
* Severe hypersensitivity or allergic reactions to study intervention components or monoclonal antibodies
* Psychiatric illness or medical condition, including recent suicidal ideation or behavior, that may increase risk or interfere with study participation
* Prior anti-angiogenic therapy or other prohibited anti-tumor or immunomodulatory therapies per protocol-specified washout periods
* Use of prohibited concomitant medications, including high-dose systemic corticosteroids, certain anticoagulants, or live vaccines within protocol-specified timeframes
* Recent participation in another investigational study (within 30 days or 5 half-lives, whichever is longer)
* Pregnant or breastfeeding participants, or unwillingness to comply with contraception requirements

• Pfizer CT.gov Call Center, Study director, Pfizer

NIH grants: 2025