Medicine Matters oncology

The bottom line from IMpassion 130 is that adding atezolizumab and nab-paclitaxel is very well tolerated. Patients live a good quality of life who respond to it. And it confers both a progression-free survival benefit as well as a clinically meaningful overall survival benefit specifically in patients with advanced disease that's PD-L1 immune cell positive. So it really is the treatment of choice for first-line therapy of advanced disease in patients with triple-negative breast cancer that's PD-L1 immune cell positive.

So IMpassion 131 was a trial of a somewhat similar design. It involved a very similar patient population. The statistical design was very different. The randomization was different and occurred at a ratio of 2:1 with twice as many patients receiving immunotherapy as the control arm.

The trial evaluated adding atezolizumab to paclitaxel, which is a drug in the same class as nab-paclitaxel, but it's bound in a different delivery vehicle. Nab-paclitaxel is albumin-bound. Paclitaxel is delivered in a cremophor in a solvent, and paclitaxel actually requires pre-treatment with steroids. So there was a much greater use of steroids in IMpassion 131 than there was in 130.

I think the delivery of the two drugs in the tumor microenvironment could potentially be different as well. We have a lot of work to do to sort through the reason for the differences in those two trials.

Of course, IMpassion 131 did not meet its primary endpoint of progression-free survival. So the opportunity we have is to analyze the samples from the patients on those trials who received the different treatments because the patient population is actually, at least in terms of eligibility criteria, quite similar.