Business Decision

This study will be conducted in adult participants diagnosed with advanced tumors to characterize the safety, tolerability, pharmacokinetics (PK), and activity of FS118. This is a Phase 1/2, multi-center, open-label, multiple-dose, first-in-human study, designed to systematically assess safety and tolerability, to identify the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) for FS118 in participants with advanced tumors and to determine the efficacy of FS118 in participants with squamous cell carcinoma of the head and neck (SCCHN) as monotherapy and in combination with paclitaxel. In addition to safety, pharmacokinetics, pharmacodynamics, immunogenicity and efficacy will also be assessed.

Inclusion Criteria:

All participants:

• Age ≥18 years;
• Participants with histologically confirmed, locally advanced, unresectable, or metastatic solid tumors that progressed while on or after PD-1/PD-L1 containing therapy;
• Measurable disease;
• Eastern Cooperative Oncology Group (ECOG) Performance Status ≤1;
• Life expectancy estimated to be at least 3 months;
• Highly effective contraception;
• Willing and able to provide written informed consent.

Expansion cohort only:

• Histologically and/or cytologically confirmed recurrent/metastatic (R/M) SCCHN that is not amenable to curative therapy by surgery or radiation;
• Only 1 prior anti-PD-1 or anti-PD-L1 therapy and documented PD-L1 scoring ≥1% by combined positive score or tumor proportion score as part of their treatment;
• An anti-PD-1 or anti-PD-L1 treatment regimen must be the last prior therapy before study enrollment, following no more than 2 prior systemic regimens for R/M SCCHN;
• Acquired resistance to an anti-PD-1- or anti-PD-L1-containing therapy;
• The participant agrees to undergo a pre-treatment and on-treatment core or excisional biopsy and the biopsy procedure is not judged to be high risk by the Investigator.

Exclusion Criteria:

All participants:

• Participant is deemed at high risk of fatal outcome in case of COVID-19;
• Participants with a history of COVID-19 and have not provided a negative test for SARS CoV-2 infection within 28 days of the planned first dose date with FS118;
• Prior therapy: Received systemic anti-cancer therapy within 28 days or 5 half-lives, of the first dose of study drug, or prior treatment with a LAG-3 inhibitor;
• Participants with active or documented history of autoimmune disease;
• History of uncontrolled intercurrent illness;
• Known infections;
• Uncontrolled CNS metastases, primary CNS tumors, or solid tumors with CNS metastases as only measurable disease;
• Prior history of or active interstitial lung disease or pneumonitis, encephalitis, seizures, severe immune related adverse events with prior PD-1/PD-L1 containing treatments;
• Significant cardiac abnormalities;
• Significant laboratory abnormalities;
• Intolerance to the investigational product or its excipients, or any condition that would significantly impair and/or prohibit the participants's participation in the study, as per the Investigator's judgment.

Expansion cohort only:

• Participant has nasopharynx or thyroid primary tumor site;
• History of severe immune-related toxicity during the prior treatment with checkpoint inhibitors.