Know why ZYBRESTAT Progression Free Survival can be a surrogate for Overall Survival
So, a woman in the treatment arm of the combo ZYBRESTAT w/Avastin P2 trial gets treated. Her ovarian cancer does not get worse during and following treatment for x amount of time. When the treatment arm is compared to the control arm of Avastin alone the statistical endpoint for the Z arm reaches its primary endpoint of PFS. OK, so there's no hard conclusion reached at that point in regards to OS, but overall survival takes much longer to conclude and ovarian cancer, in this case, is a killer with a very high mortality rate, so postulating whether these results can be a surrogate for OS is a big deal. Was quality of life affected by Z? Z is non toxic and its side effects are easily treated, so right there, I would say that quality of life saw no negative impact especially compared to toxic chemo alternatives.. So if disease does not get worse during and after treatment enough so that the PFS primary endpoint was stat significant (the control of the cancer is not resulted in by way of a toxic side effect to the patient's overall health) and quality of life is not a negative, then IMO, ZYBRESTAT PFS results will be viewed by deciding approval bodies as an acceptable surrogate for overall survival.
Avastin was approved for ovarian cancer in EU in 2011 on PFS endpoint. Further follow up showed OS trending higher, but not conclusive. Results in October 2013 in a large advanced ovarian cancer trial showed patients treated w/Avastin plus chemo lived over 9 months longer than those treated with just the chemo. Why I'm very hopeful of Z is that it improves on the PFS of Avastin in this disease, which has already shown that its PFS results ARE a surrogate for OS by way of those UK results. All IMO only.