Robert K. emails: "If you get a chance could you take a quick look at Advaxis (ADXS). Something just isn't adding up. Thanks for your time."
Advaxis lead product ADXS-HVP is a "cancer vaccine" consisting of listeria bacteria engineered to produce antigens that are supposed to stimulate the patient's immune system to recognize and kill cancer cells associated with HPV.
Last fall, Advaxis announced results from a phase II study of ADXS-HVP in patients with recurrent cervical cancer. The study was randomized but not in a way that allows for the best assessment of the vaccine's efficacy: 110 women with recurrent cervical cancer were all treated with ADXS-HVP but half the women were also administered the chemotherapy drug cisplatin.
What you'd rather see in this phase II study is half the cervical cancer patients treated with ADXS-HVP plus cisplatin and the other half treated with cisplatin alone as a true control arm.
The results: No difference in overall survival between the two arms of the study, with median overall survival of 8.5 months. At 12 months, 36% of patients across both arms were alive; at 18 months, 28% of patients were alive. The overall response rate for all 110 patients was 11% -- again, no difference between the two treatment arms.
Advaxis described these phase II data last November as "encouraging" and supportive of moving ADXS-HPV into more advanced clinical trials. The reason given for optimism was a comparison of the ADXS-HPV data to a 2004 phase III study by Moore et al which compared cisplatin to cisplatin and paclitaxel in patients with recurrent cervical cancer.
The Moore study reported median overall survival of 8.9 months for cisplatin versus 9.9 months for cisplatin/paclitaxel -- a difference that was not statistically significant. Response rates were 19% for cisplatin and 36% for cisplatin/paclitaxel.
An objective comparison between these two studies doesn't exactly justify the optimism which Advaxis claims to see in the ADXS-HPV data. If the vaccine were truly effective, we should be seeing a stronger synergistic effect between ADXS-HPV and cisplatin. Instead, we see a median overall survival of 8.5 months for ADXS-HPV plus cisplatin in the Advaxis study compared to 8.9 months for cisplatin alone in the Moore study. Not exactly confidence inspiring.
One more important distinction between these two studies: Advaxis conducted its phase II study of ADXS-HPV entirely in India, while the Moore study was conducted in the United States by leading academic institutions. The latter study has more credibility.
Unfortunately, I'm not sure Advaxis' next step with ADXS-HPV will tell us much more about the vaccine's efficacy. An ongoing, U.S.-based phase II study is set up to enroll only 67 patients with recurrent cervical cancer. The study isn't randomized and has no control arm.