A Phase I Study of TAS3681 in Men with Metastatic Castration-Resistant Prostate Cancer


Full Title

A Phase 1, Open-Label, Non-Randomized, Safety, Tolerability, and Pharmacokinetic Study of TAS3681 in Patients with Metastatic Castration Resistant Prostate Cancer


Prostate cancers initially need the male hormone testosterone for growth. Hormone therapies that lower the level of testosterone are among the most effective treatments for prostate cancers that have spread to other organs (metastasized). The benefits of hormone treatments do not last, however. Over time, many prostate cancers continue to grow despite hormonal therapies; these are called “castration-resistant prostate cancers” (CRPC).

The androgen receptor is a protein that is important in the development and progression of prostate cancer. TAS3681 is an investigational drug designed to inhibit prostate cancer growth by blocking the androgen receptor. It is hoped that TAS3681 can make prostate cancer cells less resistant to standard therapies.

In this study, researchers are finding the highest dose of TAS3681 that can be given safely in men with metastatic CRPC. TAS3681 is taken orally (by mouth).


To be eligible for this study, patients must meet several criteria, including but not limited to the following:

  • Patients must have metastatic CRPC that continues to grow or cannot be treated with abiraterone and/or enzalutamide as well as chemotherapy.
  • At least 4 weeks must pass between completion of prior therapies and entry into the study.
  • Patients must be physically well enough that they are fully ambulatory, capable of all self care, and are capable of all but physically strenuous activities. As an example, patients must be well enough that they would be able to carry out office work or light housework.
  • This study is for men ages 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Dana Rathkopf at 646-422-4379.