Cabozantinib works at lower dose, and after Abiraterone or Cabazitaxel

[JimJimJimJim]

Jim Marshall (not a doctor) said ...

Cabozantinib, an experimental drug, has shown strong activity in castrate resistant prostate cancer. On bone scans, tumor shrinkage in one study was seen in 76% of men.

However, the side effects of 100 mg per day were so strong that many men stopped using the drug, or reduced the dose.

So, two new studies looked at lower doses.

Basically:

• 40 mg per day gave good bone scan results, with much fewer side effects; and
  
• 20 mg per day did not give good bone scan results.
  

The response was just as good whether or not the men had had abiraterone (Zytiga) and/or cabazitaxel (Jevtana).

Further trials of Cabozantinib have been started.

... end Jim

Cabozantinib ... produced responses in 76% of men with metastatic castration-resistant prostate cancer (CRPC) in a previous phase II discontinuation trial. At the daily dose of 100 mg, however, 51% of patients required dose reductions and 10% stopped using the drug completely because of significant toxicities.

... a bone scan response was achieved in 16 of 24 patients (67%) receiving cabozantinib 40 mg.

... Cabozantinib 20 mg daily was less active than the 40-mg dose, with only 1 of 10 evaluable patients achieving a response at week 6.

... The median duration of response was 5.4 months, and activity occurred regardless of prior abiraterone (Zytiga) and/or cabazitaxel (Jevtana) therapy. Among 62 evaluable patients, 39% converted to less than 5 CTCs per 7.5 mL of blood. [jm: CTC = Circulating Tumor Cells]

... Two phase III studies have recently been initiated. COMET-1 is comparing 60-mg daily cabozantinib vs. twice-daily 5-mg prednisone in metastatic CRPC that progressed after docetaxel and abiraterone (Zytiga) and/or MDV3100. COMET-2 is comparing cabozantinib vs. mitoxantrone (Novantrone) plus prednisone in previously treated, symptomatic CRPC.

[Mitoxantrone is sometimes spelt mitozantrone]