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Cabozantinib works at lower dose, and after Abiraterone or Cabazitaxel


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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.


  • 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]

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