Sponsor: Pfizer (industry)
Phase: 2/3
Start date: Feb. 6, 2026
Planned enrollment: 840
PF-08634404 (SSGJ-707) is an investigational bispecific antibody being studied for advanced cancers, including non-small cell lung cancer (NSCLC). Human phase 2 results have been reported, but the evidence remains preliminary: the principal findings are from conference abstracts, and a phase 3 NSCLC trial is intended to test the treatment more definitively. (ascopubs.org)
The antibody binds both PD-1, an immune checkpoint, and VEGF, a driver of blood-vessel growth. It is designed to combine PD-1 blockade with VEGF inhibition in one molecule. (ascopubs.org)
In the NSCLC monotherapy study, 42.2% of 83 patients across dose groups had a treatment-related adverse event of grade 3 or higher. The most frequent were pneumonia (8.4%), hypertension (7.2%), and coughing up blood (hemoptysis; 6.0%). In the NSCLC chemotherapy study, grade 3 or higher treatment-related events occurred in 39.0% of patients receiving the 10 mg/kg SSGJ-707 regimen, versus 32.8% receiving tislelizumab; three treatment-related deaths were reported in the SSGJ-707 group, including two attributed to hemoptysis. Safety estimates may change with larger studies and longer follow-up. (ascopubs.org)
Last updated: Sep 2026
Goal: Assess the safety and antitumor activity of PF-08634404 plus chemotherapy as first-line treatment for advanced gastroesophageal adenocarcinoma, then compare its efficacy with nivolumab plus chemotherapy.
Patients: Adults with locally advanced or metastatic gastric, gastroesophageal junction, or esophageal adenocarcinoma; HER2-negative and PD-L1-positive disease; ECOG performance status 0–1; and no prior systemic therapy for advanced disease. Key exclusions include active CNS metastases, significant bleeding risk, recent major surgery, clinically significant cardiovascular disease, active autoimmune disease requiring systemic treatment, and interstitial lung disease or pneumonitis.
Design: Two-part phase 2/3 study. Phase 2 evaluates PF-08634404 plus chemotherapy for response and safety; the randomized phase 3 portion compares that regimen with nivolumab plus chemotherapy. Treatment is given in repeated cycles.
Treatments: PF-08634404 (SSGJ-707) is an investigational bispecific antibody targeting PD-1 and VEGF, designed to combine immune-checkpoint blockade with inhibition of tumor-associated blood-vessel growth. Preliminary phase 2 NSCLC data have shown responses, including a 58.6% confirmed response rate with PF-08634404 plus chemotherapy versus 38.7% with tislelizumab plus chemotherapy in small nonsquamous cohorts; these results do not establish benefit in gastroesophageal cancer. Serious bleeding, including fatal hemoptysis, has been reported in early studies. Nivolumab is an approved PD-1 inhibitor given with chemotherapy as the active comparator.
Outcomes: Phase 2 primary measures are investigator-assessed confirmed objective response rate by RECIST 1.1 and treatment-emergent adverse events. Phase 3 primary measures are blinded independent central review–assessed progression-free survival and overall survival. Secondary measures include response and duration of response, additional survival measures, safety and laboratory abnormalities, PF-08634404 pharmacokinetics and anti-drug antibodies, and gastric cancer–specific quality of life.
Burden on patient: Moderate to high. Repeated treatment cycles and oncology visits, imaging for response assessment, laboratory and safety monitoring, and follow-up require ongoing time and travel. Participants receiving PF-08634404 also have predose and postdose blood sampling for pharmacokinetics and anti-drug antibodies; phase 3 participants complete quality-of-life assessments. No mandatory research biopsy or exact visit schedule is specified.
Last updated: Sep 2026
Inclusion Criteria:
* Histological or cytological confirmed gastric, gastroesophageal junction or esophageal adenocarcinoma.
* Evidence of locally advanced or metastatic disease.
* Eastern Cooperative Oncology Group performance status (ECOG) 0-1
* No prior systemic therapy for advanced or metastatic disease.
* Adequate hepatic, liver, and renal function
* HER-2 negative status based on local testing
* PD-L1 positive status based on local testing
Exclusion Criteria:
* Participants with known active CNS metastases, including leptomeningeal, brainstem, meningeal, or spinal cord metastases or compression
* Clinically significant risk of hemorrhage or fistula
* Major surgery or severe trauma within 4 weeks prior to the first dose, or planned major surgery during the study
* History of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation.
* Any Grade ≥3 bleeding/hemorrhage events within 28 days of Cycle 1 Day 1, or prior history of clinically significant bleeding events
* Clinically significant cardiovascular disease, or other comorbidities, within 6 months prior to first dose
* Participants with active autoimmune diseases requiring systemic treatment within the past 2 years
* Evidence of non-infectious or drug-induced interstitial lung disease (ILD) pneumonitis
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