This research study is a Phase II clinical trial, researching the effectiveness of the combination of telaglenastat and talazoparib in participants with metastatic castration-resistant prostate cancer (mCRPC).~The U.S. Food and Drug Administration (FDA) has not approved telaglenastat or the combination of telaglenastat and talazoparib as a treatment for any disease.~The FDA has not approved talazoparib for metastatic castration-resistant prostate cancer (mCRPC) but it has been approved for other uses.~Telaglenastat is a drug designed to stop cancer growth by blocking glutaminase activity. Glutaminase is an enzyme in the body that is overproduced by some cancers and can fuel cancer growth. Telaglenastat can lower or block glutaminase and may slow the growth or spread of some cancers.~Talazoparib is a drug that interferes with the repair activity of proteins called poly adenosine diphosphate ribose polymerases (PARP), which are found in normal and cancer cells and are involved in the repair of DNA - the genetic material found in every cell. This interference may lead to increased amounts of DNA defects and cancer cell death which may help to slow the growth of cancer cells.~The research study procedures include screening for eligibility and study treatment including evaluations and follow up visits.~There are different points in this study in which participation will start. The first group of participants will receive the combination of telaglenastat and talazoparib for the entirety of the study. If telaglenastat plus talazoparib is beneficial to the first group this will lead to the enrollment of the next group, since telaglenastat as a single drug has not been evaluated in prostate cancer. The next group will receive telaglenastat alone with the addition of talazoparib if the disease gets worse.~It is expected that about 30 people will take part in this research study.
The purpose of this research is to test the effectiveness of an experimental drug combination for people with metastatic castration-resistant prostate cancer (mCRPC).~The names of the study drugs involved in this study are:~Telaglenastat (CB-839)~Talazoparib