Onvansertib in treatment of abiraterone-resistant mCRPC

We hear that an investigational drug called onvansertib — a so-called polo-like kinase 1 (PLK1) inhibitor — may have benefit in the treatment of men with metastatic, castration-resistant prostate cancer (mCRPC) who are showing early signs of progression on treatment with abiraterone acetate (Zytiga) + prednisone.

The relevant data come from a small, Phase II clinical trial, and so we have to be cautious about the interpretation of the available data because they are based on just 26 evaluable patients (to date). However, we are all aware that improvements are urgently needed for the treatment of men with mCRPC, so even relatively small improvements from new drugs are potentially exciting.

According to a report in the Urology Times, when men with mCRPC who were showing early signs of disease progression on standard treatment with abiraterone acetate + prednisone had onvansertib added to their ongoing treatment with abiraterone + prednisone:

  • At 12 weeks of follow-up
    • 8/26 patients (31 percent) achieved full disease control (with no further PSA progression)
    • An additional 14/26 patients (54 percent) had stable disease
  • At 7 months of follow-up
    • 8/14 patients who had stable disease at 12 weeks still had stable disease

A total of 39 patients had been treated with the combination of abiraterone + prednisone + onvansertib at the time of this presentation. This included 13 patients (33 percent) with visceral metastases and 33 patients (85 percent) with bone metastases.

These patients have been treated with three different dose levels of onvansertib to date, and there is a significant risk for Grade 3 and Grade 4 side effects, of which neutropenia appears to be the most common (in up to 10 patients to date).

Clearly we will need to see a great deal more data from clinical trials before onvansertib could be submitted to regulatory authorities like the US Food and Drug Administration (FDA) for approval for routine clinical use in the treatment of prostate cancer. On the other hand, onvansertib appears to be the first of yet another new class of drugs that has the potential for treatment of advanced prostate cancer.

One Response

  1. Please be aware of the positive outcome of TheraP trial of patients resistant to airaterone and docetaxel.

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