Gregory M. Glenn
Analyst · Piper Jaffray
Yes, so this is Greg here. So thanks for the question, Ted. So the maternal immunization, as we mentioned, we expect to have a meeting with the FDA, provide them with a data package on the product, the clinical data, et cetera and we provided them our draft protocol, what we expect to do in the fall. And assuming that we agree on the PATH forward, we expect to do a trial on pregnant women. It will be a relatively small trial. It'll be -- we propose 50 subjects, 25 placebo, 25 active, where we'll immunize in the third trimester. Based on the dose, we have determined on the study and we will follow the children through an RSV season. So that will be the safety evaluation, safety in pregnancy for active immunization and safety of the children after having received the antibodies passively. I think things that are -- would be really important highlights, I would say really landmark data for vaccinology will be to observe the induction of the antibodies we measure in mothers and their induction, their transmission transplacentally to infants. And as you know, after its physiologic mechanism with other vaccines, we see very robust transmission, certainly, antibodies at the level of the mother until we'd expect to see the palivizumab-like antibodies will appear in the infant. And I think that will be a very important end, I would say, landmark finding in vaccinology to be able to create this type of antibody activity in infants. If it is on the order of the level of antibodies we saw in this trial, which I will just point out that our vaccine has performed very consistently, that we would be transferring antibodies in the order of 400 micrograms per ml to infants. I think that would be really very interesting and important finding in that trial. And then, we expect to do a limited -- in kinetics to watch the decay of antibodies in infants, so we do some aluminum sampling at the sero and hopefully describe [indiscernible], and therefore, determine to what degree you might expect the protection to last. How long through infancy. So that will be a very important trial establishing the safety. I would say just as an side, there was a previous F-protein use in pregnant women. So from a risk standpoint in this population, we won't be doing something new. But this will be a vaccine where it's a recombinant protein [indiscernible] palivizumab-like antibodies. Assuming that, that trial goes forward and we observe what we expect to observe the following year, then we would go on to a larger trial, where we'd be exploring the efficacy of the vaccine in infants in third trimester immunization and looking for the reduction of medically attenuated RSV disease, as proven by PCR in a larger population. So that's sort of, I think, the horizon in which we're discussing in terms of maternal immunization with the RSV F vaccine. So with respect to the combination vaccine, we expect to take the current quadrivalent vaccine that we're manufacturing and bedside mix that with the RSV F vaccine and there really will be a safety and immunogenicity trial in healthy adults and elderly and we expect that to be a relatively small trial. But since we know a lot about the immune response, we think that the RSV F immune response we measure and neutralizing antibodies with palivizumab, as well as the HAI titers from the flu, all these are meaningful measures of immunogenicity that can be associated with protection. We think the immunogenicity trial will be very informative. And again, we expect to see the -- sort of antibody levels we've seen in our previous trial for RSV F and our flu vaccine. So then this exercise in women of childbearing age is very informative. It really helps guide our thinking on the combination vaccine and, as we mentioned earlier, on what we would do in pediatrics. So it's a tremendous data set, both safety and immunogenicity that gives us guidance on formulation and dosing choices.