This is an Open-label, multicenter clinical study conducted in two Phases to establish the efficacy, safety, tolerability, and pharmacokinetics of the ataxia telangiectasia mutated and Rad3-related protein kinase (ATR) inhibitor Tuvusertib in Combination with Cemiplimab in Participants with Non-Squamous Non-Small Cell Lung Cancer (nsqNSCLC) that has Progressed on Prior Anti-PD-(L)1 and Platinum-based Therapies..

Inclusion Criteria:

• Participants who are diagnosed with nsqNSCLC histologically or cytologically confirmed

• Participants with Radiologically confirmed/documented disease progression during or after the following systemic therapies (all required):

  • At most, 1 line of anti-PD-(L)1 therapy for locally advanced or metastatic disease. Rechallenge with the same anti-PD-(L)1 for disease considered sensitive to anti-PD-(L)1 therapy (e.g. after a treatment break) is considered 1 line
  • Platinum-based therapy for locally advanced or metastatic disease, given in combination or sequentially with anti-PD-(L)1 therapy. Participants who received adjuvant platinum-based therapy meet this criterion if disease progression occurred within 6 months from the last dose that the participant received that therapy. No additional cytotoxic therapies after progression on platinum-based therapy are allowed
  • Prior best overall response of stable disease or better with anti-PD-(L)1 therapy
  • Disease progression must have occurred while the participant has been receiving anti-PD-(L)1 therapy or within 16 weeks of the last dose of anti-PD-(L)1 therapy

• Participants with Measurable disease per RECIST v1.1

• Participants with Eastern Cooperative Oncology Group (ECOG) PS 0 or 1

• Adequate hematological, hepatic, and renal function as defined in the protocol.

• Phase 2a part only: central liquid biopsy analysis of tumor molecular alterations with an assay with appropriate regulatory status

• Other protocol defined inclusion criteria could apply

Exclusion Criteria:

• Participants with tumors harboring actionable epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) genomic aberrations. Participants with tumors with other actionable aberrations are eligible and allowed to have received up to 1 line of available targeted therapy
• Participants with history of additional malignancy within 3 years before the date of enrollment. Exceptions are squamous and basal cell carcinomas of the skin and carcinoma in situ of the cervix, or malignancy that in the opinion of the Investigator, with concurrence of the Sponsor's Medical Monitor, is considered cured with minimal risk of recurrence within 3 years
• Participants with known brain metastases, unless clinically stable
• Participant with history of (noninfectious) pneumonitis that required systemic corticosteroids or current pneumonitis/interstitial lung disease
• Other protocol defined exclusion criteria could apply

We are committed to enhancing public health through responsible sharing of clinical trial data. Following approval of a new product or a new indication for an approved product in both the US and the European Union, the study sponsor and/or its affiliated companies will share study protocols, anonymized patient data and study level data, and redacted clinical study reports with qualified scientific and medical researchers, upon request, as necessary for conducting legitimate research. Further information on how to request data can be found on our website bit.ly/IPD21