A Phase Ib Study of Enzalutamide plus Ribociclib in Men with Advanced Prostate Cancer


Full Title

Randomized Phase IB/II Study of Enzalutamide With and Without Ribociclib in Patients with Metastatic Castrate Resistant, Chemotherapy Naïve Prostate Cancer that Retains RB Expression


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).

Enzalutamide is a standard drug used to treat CRPC. It works by blocking a protein called the androgen receptor. Researchers want to see if adding the drug ribociclib to enzalutamide treatment is more effective than enzalutamide alone. Ribociclib blocks enzymes that prostate cancer cells need called cyclin-dependent kinases (CDKs). It is approved for treating advanced breast cancer; its use in this study is considered investigational.

In this part of the study, researchers are assessing different doses of ribociclib to give in combination with enzalutamide. Both drugs are 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 is positive for a protein called RB. Ribociclib only works against RB-positive tumors.
  • Patients must have rising PSA or disease growth despite hormonal therapy.
  • Prior chemotherapy or treatment with enzalutamide or abiraterone acetate is not permitted.
  • 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 age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Susan F. Slovin at 646-422-4470.