This study is being done to evaluate the safety and potential effectiveness of BHV-1510 alone and BHV-1510 in combination with cemiplimab in participants with certain solid tumor cancers. This study will be conducted in 2 parts called “phases.”

BHV-1510 is considered investigational, which means it has not been approved by the U.S. Food and Drug Administration (FDA). This is the first time BHV-1510 will be given to humans. 
   
This study where BHV-1510 is given alone is for participants who may have previously been treated with most available treatment options that are considered standard and appropriate by the treating doctor for their type of cancer. These treatments may have stopped working or are not feasible and the treating doctor is recommending this study. Participants receiving BHV-1510 in combination with cemiplimab may be receiving treatment for the first time or this may be prior to being treated with all other available treatment options. 
   
Phase 1

• Participants in Phase 1 will have one of the following types of cancers: Endometrial, Ovarian, Cervical, Gastric/ Gastroesophageal junction (GEJ), Small Cell Lung Cancer (SCLC), Extensive-stage SCLC (ES-SCLC), squamous or non-squamous non-small cell lung cancer (NSCLC), Urothelial, Triple Negative Breast Cancer (TNBC), or Endometrial (pMMR only).
• The goal of Phase 1 is to determine the safety and side effects of BHV-1510 when it is given with or without cemiplimab to determine the best dose(s) and best dosing schedule(s) to be used for further study.  

Phase 2

• Participants in Phase 2 will have one of the following types of cancers: Endometrial, Ovarian, Cervical, Gastric/GEJ, Small Cell Lung Cancer (SCLC) or non-small cell lung cancer (NSCLC), Urothelial, Triple Negative Breast Cancer (TNBC) or they have an epithelial tumor and have been treated with a Post-TROP2 drug or a drug called Enhertu®.
• In Phase 2, particiapnts will receive the best dose and best dosing schedule of BHV-1510 as determined in Phase 1. The goal of Phase 2 is to test if BHV-1510 is effective in treating these cancers.