A Phase 1/2 Study of FS118 in Patients With Advanced Malignancies

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.