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Novavax, Inc. (NASDAQ:NVAX)

RSV Vaccine Candidate Phase II Top Line Results Conference

April 03, 2013 10:00 am ET

Executives

Frederick W. Driscoll - Chief Financial Officer, Principal Accounting Officer, Vice President and Treasurer

Stanley C. Erck - Chief Executive Officer, President , Director and Member of Finance Committee

Gregory M. Glenn - Chief Medical Officer and Senior Vice President

Pedro Piedra

Louis Fries - Vice President of Clinical and Medical Affairs

Analysts

Gregory R. Wade - Wedbush Securities Inc., Research Division

Edward A. Tenthoff - Piper Jaffray Companies, Research Division

Kevin DeGeeter - Ladenburg Thalmann & Co. Inc., Research Division

Elemer Piros - Burrill & Company

George B. Zavoico - MLV & Co LLC, Research Division

Operator

Good day, ladies and gentlemen, and welcome to the Novavax RSV Vaccine Candidate Phase II Top Line Results Conference Call. My name is Karen, and I'll be your coordinator for today. [Operator Instructions] As a reminder, this conference is being recorded. Novavax, please proceed with your call.

Frederick W. Driscoll

Thank you, Karen, and good morning, everyone. This is Fred Driscoll, Chief Financial Officer of Novavax, and I thank you for joining us on today's conference call to discuss the top line results from Novavax's Phase II clinical trial of our RSV-F vaccine candidate in women of childbearing age. Both the press release from yesterday and an archive of this call can be found on the company's website at novavax.com.

On today's call are Novavax President and Chief Executive Officer, Stan Erck; our Senior Vice President and Chief Medical Officer, Dr. Gregory Glenn; and Dr. Louis Fries, our Vice President of Clinical and Medical Affairs; and Dr. Tony Piedra, Professor from the Department of Molecular Virology and Microbiology at Baylor College of Medicine.

Before we begin our prepared remarks, I need to remind you that we will be making forward-looking statements during this teleconference that could include financial, clinical or commercial projections. Statements relating to future financial or business performance, conditions or strategies and other financial and business matters, including clinical developments and anticipated milestones, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act. Novavax cautions that these forward-looking statements are subject to numerous assumptions, risks and uncertainties which change over time. Further, information on the factors and risks that could affect Novavax's business, financial conditions and results of operations are contained in Novavax's filings with the SEC, which are available at www.sec.gov. These forward-looking statements speak only as of the date of this call, and Novavax assumes no duty to update such statements.

I'll now turn the call over to Novavax's President, Stan Erck.

Stanley C. Erck

Thanks, Fred, and good morning, everyone. So last night, we issued a press release announcing positive top line results from our Phase II study of our RSV-F vaccine candidate in women of childbearing age. We were very pleased that the vaccine achieved the trial's clinical protocol specified objectives. The primary objectives of the study were fourfold: first, to monitor safety; second, to measure the difference in anti-F IgG elicited across doses of 60 micrograms or 90 micrograms of our RSV antigen; third, to evaluate the use of 1 versus 2 immunizations; and finally, to evaluate the use of aluminum phosphate or alum as an adjuvant.

Overall, the results from this trial suggests that our RSV-F vaccine candidate has a potential to induce safe and clinically useful immunity for this important patient population. Significantly, immune responses in this study also equaled or exceeded those seen in our previous Phase I study.

The results from this study provide a compelling rationale for continued development of our RSV vaccine candidate. As you can imagine, these results will only increase our excitement regarding our RSV program. These data represent another key step in the development of our RSV vaccine candidate for use in the maternal immunization strategy.

With this trial, we have now expanded our safety database and have treated almost 500 subjects to date without a vaccine related serious adverse event. As you know, safety is paramount in the development of any vaccine, and we were pleased by the profile of our candidate.

As Greg will discuss shortly, the immunogenicity results from this Phase II trial confirm that the vaccine contains a potent antigen with the potential of inducing clinically meaningful immunity. This is very important as we move forward in the maternal immunization strategy, in which antibodies in vaccinated women can be expected to be naturally transferred to their infants in utero, potentially conferring protection at the earliest stage of life when these infants are extremely vulnerable to severe respiratory disease due to RSV. Maternal immunization is already commonly performed in the clinic to protect both the mother and infant from influenza, pertussis and tetanus.

Before I turn the call over to Greg to review the trial and then to Dr. Piedra to put the results in perspective, I want to first acknowledge and thank our partners at PATH. PATH is an international nonprofit organization that supports the development of health care initiatives for low resource countries. PATH is committed to the development of an RSV vaccine and to maternal immunization in order to protect vulnerable infants from RSV.

The collaboration with PATH provided approximately $2 million of non-dilutive initial funding to support this study. And as part of our agreement with PATH, they can elect to continue to collaborate on additional clinical phases to develop a vaccine for maternal immunization, potentially funding 50% of Novavax's external clinical development costs all the way through to licensure.

With that, I'll turn the call over to our Chief Medical Officer, Greg Glenn.

Gregory M. Glenn

Thank you, Stan, and good morning. I'm going to give a brief top line summary of the safety and immunogenicity results.

So this clinical trial was initiated in early October of last year and was fully enrolled in less than 2 weeks. This Phase II trial was a randomized blinded placebo-controlled trial designed to evaluate the safety and immunogenicity of 2-dose levels of our RSV-F vaccine candidate with and without aluminum as adjuvant. The study enrolled 330 non-pregnant women of childbearing age. In total, there were 9 cohorts with 30 subjects each -- in each actively treated cohort and 60 subjects that received a placebo. Subjects in the active cohort received 60 and 90 micrograms of the antigen, both with or without the aluminum adjuvant at day 0. Half the cohorts also received a second injection at day 28. Also, one of the cohorts mimicked the Phase I vaccine formulation for comparison purposes with subject receiving 60-microgram dose at both day 0 and day 28 with aluminum phosphate adjuvant.

The data discussed today covers results from the trial through day 56 observations. Safety will continue to be evaluated over a total of 6 months and immunogenicity for 4 months for each participant.

As Stan mentioned earlier, the protocol specified objectives were met, and immune responses were -- observed in this Phase II clinical trial were equal or exceeded those seen in our previous Phase I clinical trial using our nanoparticle vaccine. In the Phase II study, peak geometric mean titers of anti-F IgG in the 2-dose aluminum adjuvant groups ranged from 12,000 to 14,000, representing a thirteen- to sixteenfold rise compared to a six- to tenfold rise in the non-adjuvant group. Minimal increases were observed by increasing antigen doses from 60 to 90 micrograms, and this is an important observation as we believe we are on the plateau of the dose response curve. And as a result, we believe that the 60-microgram dose is the antigen dose we'll look forward with. The use of aluminum adjuvant enhanced both the single- and 2-dose regimen of the anti-F IgG responses, with the greatest responses observed using a 2-dose regimen.

With respect to secondary and exploratory objectives, the peak geometric mean RSV-A neutralized antibodies in aluminum adjuvant groups ranged from a log2 9.5 to 10.5, representing a 3.1 to 3.8 geometric mean rise, while the median titers rose approximately fourfold.

Our clinical assays in the preclinical challenge studies have linked the protective effects of palivizumab with palivizumab-like immunity induced by our vaccine candidate. Palivizumab-like antibodies rose eight- to ninefold, with significant titer rises in greater than 40 -- greater than 92% of vaccinees in the 2-dose aluminum adjuvanted groups. As a reminder, palivizumab is a licensed molecule antibody marketed as Synagis that is used to prevent high-risk infant hospitalization due to RSV. The results from the current trial replicated the immunogenicity results in the Phase I trial, and we observed again that our vaccine candidate induce robust palivizumab-like antibodies.

Now turning to safety. The vaccine was well tolerated, and the safety profile was similar to that observed previously in our Phase I clinical trial. Principal adverse event observed was transient mild to moderate injection site pain, which is predictably somewhat more frequently in the -- frequent in the adjuvanted vaccine recipients. There was no clinically important difference in the systemic reactogenicity that was comprised mainly of mild to moderate headache, fatigue, muscle ache, which are frequently known after treatment by many vaccines. There are no difference in the safety assessments across doses or worsening of reactogenicity with second dose. Laboratory testing did not reveal any clinically significant changes in normal blood chemistries or hematology parameters.

I'm not going to provide any additional data this time as we expect to present this data at an upcoming scientific meeting. Overall, we are extremely pleased with the results. We believe that they provide a strong rationale for continuing development of our RSV vaccine candidate. We've answered key questions regarding the dose regimens and the use of aluminum phosphate as adjuvant.

Now before I turn this call over to Dr. Piedra, I want to remind investors that we have a Phase I dose ranging clinical trial of our RSV vaccine at elderly patients ongoing. This trial, which is fully enrolled, is a randomized blindly controlled study that will evaluate the immunogenicity and safety of 2 doses of our RSV candidate with or without aluminum as an adjuvant. The study enrolled 220 adults, 60 years of age and over, who received a single muscular -- intramuscular injection of our RSV vaccine or a placebo plus a single dose of the licensed influenza vaccine or a placebo at day 0 and 28.

Safety and immunogenicity will be evaluated for up to 1 year, and we expect to report top line results from that trial later in the second quarter of this year. Once we've reviewed the data from the elderly trial and in combination with our findings from the Phase II trial in women of childbearing age, which we are reporting on today, we will provide at that time an update on the next steps in the clinical development plan for the RSV program.

With that, I'll now turn the call over to Dr. Piedra from Baylor College of Medicine, who's a recognized leader in the field of RSV, to put the Phase II data that I have discussed into perspective. Dr. Piedra?

Pedro Piedra

Thank you, Greg, and good morning. From my perspective, there are 3 important conclusions that can be drawn at this time, although it is important to note that the study is still ongoing. First conclusion, there were no unexpected safety signals. Overall, Novavax RSV vaccine was safe and well tolerated in healthy women of childbearing age. Second conclusion, the safety and immunogenicity profiles of Novavax RSV vaccine was consistent with the data generated in the Phase I healthy adult study. Consistency is good because it demonstrates the production process is able to generate comparable products over time. And the third conclusion, which has already been commented on, and that is that the objectives of the trial were met. The various RSV-F vaccine formulations were safe, well tolerated and immunogenic. And now, an optimal vaccine formulation can be chosen for pregnant women clinical trial.

Overall, I am reassured with the safety and immunogenicity profiles of Novavax RSV-F vaccine and its potential to move forward into a pregnant women clinical trial.

And that's my perspective, and now will like to turn it back to Stan for closing remarks.

Stanley C. Erck

Thanks, Tony. So now with positive Phase II data now in hand, we believe we'll remain clearly in the lead position in the development of an RSV vaccine. We continue to see tremendous excitement regarding the RSV program, both internally and externally. We look forward to presenting the full data set from the study in the future at a scientific conference.

As Greg mentioned regarding our next steps in the development of our RSV vaccine, we want to take a measured approach and assimilate all the clinical data from our Phase I clinical trial, this current Phase II trial in women of childbearing age and soon-to-be released data from the elderly trial. And at that time, we will assemble and provide a clinical pathway for the program going forward.

That concludes our prepared remarks, and operator, let's open up the call for questions.

Question-and-Answer Session

Operator

[Operator Instructions] Our first question comes from the line of Greg Wade from Wedbush.

Gregory R. Wade - Wedbush Securities Inc., Research Division

Greg or Dr. Piedra, I'm wondering, do the kinetics of the antibodies, the flu, pertussis or tetanus, in women of childbearing age, are they predictive of protection to the infant? And then just a quick follow-up. I guess, reproductive toxicology is probably a rate limiting step to getting into pregnant women. Maybe just give us an indication as to when that preclinical work will be completed.

Gregory M. Glenn

So I'll take the second question, and I'll let Dr. Piedra take the first question. So we are going to conduct a reproductive toxicology study that will be a precursor for going into pregnant women. As Stan discussed, we haven't really disclosed our ongoing plan at this time. That is an important step we'll take before getting into this target population. And I'll turn the first part of that question over to Dr. Piedra.

Pedro Piedra

With regards to the kinetics of the immune response, I have more data with influenza, where it demonstrates that if you have a significant rise and you're able to improve antibody response in a short time, you know that the offsprings, the babies, will be protected against influenza during a certain time period. And for Mark Steinhoff's study that was conducted in Bangladesh, they were able to observe protection for up to 6 months. For tetanus, we are truly aware that neonatal tetanus, which is really a disastrous disease to have, has been prevented [indiscernible] measure through maternal immunization with tetanus. With regards to kinetics of antibody response, I'm not familiar with that. And with regards to pertussis, that is now a recent recommendation for women to receive the acellular pertussis vaccine in order to reduce mortality in the first few months of life if an infant comes down with pertussis. And that is a strategy that has recently been implemented. Know that women have waning immunity, and thereby, maternal immunization is able to boost that antibody response and provide it to the infant.

Gregory R. Wade - Wedbush Securities Inc., Research Division

Yes. If I just could ask a follow-up, is it pretty universal that the antibodies developed in the pregnant mother are all transferred to the fetus? Or is there some hit-and-miss there?

Pedro Piedra

The data suggests in particular for protein vaccines that what the mother -- the level of antibodies that the mother has will be very comparable to the level of antibodies that the infant will receive. So if one is able to really boost the antibody responses in the mother, the infant will be able to receive that antibody if the vaccine is administered at an appropriate time in the third trimester or second trimester.

Operator

And our next question comes from the line of Ed Tenthoff from Piper Jaffray.

Edward A. Tenthoff - Piper Jaffray Companies, Research Division

So I guess, maybe more of a kind of [indiscernible] question. With this good data in hand and obviously, you have I think the elderly data coming within the next couple of months, if I'm not mistaken, what are your longer-term plans here for the RSV vaccine? Is this something that you guys intend to keep yourselves, take further along and create more value for shareholders? I mean, obviously this is a very interesting program for big pharma. So is this something you would want to partner near term or take further along yourselves?

Stanley C. Erck

Ted, it's a great question. It's something we think about quite a bit over the past year or 2 since we'd first gotten the data from the Phase I trial and how we want to go forward. I think that we've concluded that we can best move the program forward by keeping control of it ourselves at least through Phase IIs and ask me in the -- in -- sometime down the future whether we take it into Phase IIIs or not. We have the capital and the financial ability to control the program at least for the next couple of years, and we plan to do that. We think we move it along, we can take it, advance it into pregnant women, into children, into the elderly on our own much faster than would be done if we had a partner. And so that's our plan. We think also that we create a lot more value for the company and for shareholders by keeping it in the company for now.

Operator

And our next question comes from the line of Kevin DeGeeter from Ladenburg.

Kevin DeGeeter - Ladenburg Thalmann & Co. Inc., Research Division

My questions actually were around how we think about antibody titer levels, not necessarily protective antibody titer levels, but what range of antibody titer levels do you think or does the literature suggest would be necessary to reduce the severity of disease in some number of newborns? Because I'm trying to appreciate whether or not the issue here or the bar we're ultimately shooting for is full protection or reduction in hospitalization and sort of severe cases of RSV among newborns.

Stanley C. Erck

Maybe, Tony, you could comment on that, and then I'll fill in the gaps.

Pedro Piedra

Okay. From my perspective and I think from the clinical need, the medical need is the reduction of severe cases. We know that the greatest rates of hospitalization occur in infants under 1 year of life. And within that group, the greatest rate really is within the first 3 to 4 months of life in which we think that if one was to use a vaccine directly to the infant at that age, it would be not a good strategy to provide protection early on. And so maternal immunization will be the best way to be able to protect those who have the greatest rate of hospitalization, and that would be infants within the first 3 to 4 months of age. And I believe that the levels that we're currently achieving with Novavax RSV-F vaccine, you're at that area. And I base that on data that we have generated in the past that suggests that if you have a neutralizing antibody level of 6 to the log2 or 1 to 64, you have about a 90% reduction in RSV-related hospitalization. And the other thing that is very promising here is that they are able -- Novavax is able to measure palivizumab-like antibodies. And the data has been very consistent with prophylaxis of palivizumab that if you achieve levels in the 40 micrograms per ml level, you're having somewhere between 80% to 50% reduction of high-risk infants in hospitalization. And the palivizumab-like antibodies that are being achieved here are really in the 100- to 200-microgram level. And so that is very reasonable to think that you're going to have about 3 to 4 months level of protection against severe RSV disease and that's hospitalized -- hospitalization.

Kevin DeGeeter - Ladenburg Thalmann & Co. Inc., Research Division

Great. And maybe as a related follow-on question, do we capture baseline RSV antibody levels in -- for the Phase II? Presumably we did, how much variation are we seeing for these women of childbearing age that are coming in, in terms of baseline? How do we think about the differences of this population in terms of baseline RSV antibody levels compared to, for example, the upcoming elderly study?

Stanley C. Erck

Again, I'll let Dr. Piedra answer that question.

Pedro Piedra

Well, I think an important contribution that this study makes in addition to safety and immunogenicity is that you're really approximating more of the population that you will be reaching when you go to a maternal immunization study, and that is that about 50% of these women of childbearing age had children. And so you would expect that their level of antibodies are going to be maybe somewhat higher than individuals like elderly adults, who may not be exposed to as much RS unless they have a lot of grandchildren, and some will. And what I'm trying to say is that despite those levels maybe being a little bit higher, the RSV-F vaccine of Novavax was able to really move, to shift the curve in a very positive way, where whatever measure you chose, whether it be a ELISA, binding antibodies to the F protein, palivizumab-like antibodies or neutralizing antibodies, we were able to move the curve significantly so that the baseline value, following immunization, was at a level that you would feel comfortable to move it forward into a maternal immunization program.

Stanley C. Erck

Okay, maybe I could add one brief comment. The palivizumab-like measure, if you look at the baseline there, as we showed in the Phase I trial, it turns out that natural infection is very poor at inducing this type of activity. And so most of the subjects in these trials are either negative or very close to negative. And what's quite, I think, important, the nanoparticle boost those antibodies very significantly and, as Dr. Piedra mentioned, to levels that you would expect could confer protection. So we think this is a very important part of the innovation of our vaccine to induce these types of antibodies that relate our program to products that are -- have been shown to work and are in practice are having a big impact on RSV disease. So that's -- and I think also a very interesting scientific and clinically important results in both of these trials.

Kevin DeGeeter - Ladenburg Thalmann & Co. Inc., Research Division

And maybe one more question, and I'll get back in the queue. We were able to answer several, I think, questions here with regard to dose schedule and formulation. I guess, the only question in our variable that's out there is potentially adjusting the level of alum in the vaccine. Is that something we're going to explore, and if so, do you think we'll explore in healthy volunteers prior to going into expectant mothers? Or how do we think about the opportunity to perhaps explore different and potentially lower doses of alum in the formulation?

Louis Fries

Yes, this is Louis Fries. And I think that we have -- in the formulation that we've used here, we've clearly used a dose of aluminum phosphate which easily absorbs all the product. And we have, in fact, the long way we can dial back on that and one of the next step we would take as we further expand the safety experience with this vaccine. Now that we've focused on -- we have a strong reason to focus on aluminum adjuvanted vaccine, the next thing we will do is try a series of formulations at which we reduce the aluminum content to find the sweet spot between retained immunogenicity and the lowest necessary exposure of aluminum. So that will be the next step in our Phase II program.

Kevin DeGeeter - Ladenburg Thalmann & Co. Inc., Research Division

And that would likely be in...

Louis Fries

And that would be done in healthy women. We would not -- we would expect to refine our formulation insofar as we possibly can before entering the pregnant population and taking another step up the risk ladder.

Stanley C. Erck

Yes, Kevin, I'll just add one more thought to that. So this could be done. We will -- we'll be starting a reproductive tox study, and we can do this additional study on dose ranging of alum in parallel with -- as we do the tox study, so it's not necessarily in sequence.

Operator

And our next question comes from the line of Elemer Piros from Burrill Securities.

Elemer Piros - Burrill & Company

Maybe a question to Greg. Greg, I know you don't want to spell out too much more data pending publication, but in a qualitative sense, talking about baseline microneutralization titers, were you -- have you had a proportion of the population that were in the bracket of less than 6 perhaps? And a follow-up to that is, were you able to move those low titer subjects into the 8 and above sort of range?

Louis Fries

Yes, this is Louis Fries again. And very briefly stated, the answer to that is yes and yes. The proportion of the population with titers less than 6 varies. It varies place to place, time to time and with the frequency of recent exposures to RSV. But one of the things that we have noted universally is that we clean those subjects out and everyone or virtually everyone has titers over, say, 8 after immunization -- 8 log 2.

Elemer Piros - Burrill & Company

And just a couple of questions to Dr. Piedra. Dr. Piedra, you worked quite extensively on the purified F protein vaccine. Now that we have a recombinant version and we have sufficient amount of data, how does the 2 compare in your assessment?

Pedro Piedra

There -- well, one -- what is comparable is that they're both F proteins, but within that, there are obvious differences. And I would say one very important one is that to date, the RSV-F vaccine of Novavax has provided very consistent immunogenicity data. And that was not observed with the purified fusion protein vaccine of, in particular, the second generation of Wyeth. And there -- we don't understand completely what happened there, but we noted that over time, the immunogenicity potential of Wyeth's purified fusion protein vaccine declined. And so stability, we believe, is an important issue. And it could have been also a process because we know that the formulations were somewhat different in the way that they were derived. And so I think one of the very pleasant stories -- well, it may not be as exciting, but to me, I think it's very relevant, and that is consistency, the ability to make a product over time even though the formulations are a little bit different and come out with very safe and immunogenic profiles that are consistent over time, and I think that's very relevant. The other thing that I believe that is we don't know whether the same would have held true with the purified fusion protein vaccine, but we do know that with Novavax RSV-F vaccine, we are able to see palivizumab-like antibody responses. And I think that is very relevant because if there is anything that we know for sure in the RSV world is that the palivizumab is able to reduce the severity of RSV disease in these highest of risk infants. And having palivizumab-like antibodies is very reassuring that one would be able to extrapolate that we will probably see comparable levels of efficacy within infants that we see the maternally derived antibodies because of this palivizumab-like antibodies. I don't know whether the PFP vaccine would have produced that because we didn't measure it at that time, but we do know that the RSV-F vaccine here does. And as Greg pointed out, that's not something that we observe following natural RSV infection, which is quite curious.

Elemer Piros - Burrill & Company

Maybe just a follow-up, and this may be a naïve question, Dr. Piedra. But has there been any studies, formal studies conducted in pregnant women with low RSV IgG titers, who subsequently gave birth? And has there been a correlation made between low maternal titers and the severity of RSV disease in infants?

Pedro Piedra

For sure, yes. There had been a series of studies, especially in the 1970s and 1980s, that show that maternally derived antibodies were protective. And I think that was really very groundbreaking information because it demonstrated that antibodies were not detrimental to disease, were actually protective against disease. And one of, I would say, my mentors, Dr. Paul Glezen, who has currently retired, demonstrated that very nicely using cord blood from -- well, cord blood collected at birth that demonstrated that infants who had the highest levels of neutralizing antibodies present in the cord blood were the ones who were, if they were hospitalized, were hospitalized at a much later time period, or if they came down with RSV infection, came down with RSV infection at a later time period compared to those that had more levels of neutralizing antibodies in their cord blood.

Elemer Piros - Burrill & Company

One last question, please. Would you recommend to conduct a study in pregnant women with low titers first, to maximize the chances of seeing a bigger impact on infants subsequently?

Pedro Piedra

Well, from my perspective, I think that would be a good discussion to generate. I generally tend to be more inclusive rather than exclusive in criterias that I would choose for a clinical trial. But I think that would have to be discussed among all the important participants in order to develop the best criteria for that particular objective of the study.

Gregory M. Glenn

Yes, this is Greg. That would be our perspective too. Very likely when we do the efficacy testing, we would do this in a general population. We wouldn't prescreen for antibody titers.

Operator

And our next question comes from the line of George Zavoico from MLV & Co.

George B. Zavoico - MLV & Co LLC, Research Division

Two questions. One, you've mentioned -- in the press release, it says that the immunogenicity will be valid for several more months for each participant. What are your expectations on the durability of the antibody response?

Gregory M. Glenn

Well, at this point we don't have data, so we're interested. Just -- but I would remind you that as we look at the product profile we're considering for maternal immunization, we're trying to, I think, replicate the current practice of giving a pertussis vaccine in the third trimester. So I think there are some windows where we could entertain a 1- or 2-dose immunization. And as you know, full-term gestation is 40 weeks and the third trimester is somewhere after 28 weeks, so we could see regimens that would be a day 0, day 56 -- or sorry, day 0, day 28 or day 0 within weeks of delivery. So long-term follow-up and long-term immunogenicity is of maybe secondary importance to the data we're sharing today. So we're interested. It's possible that if we had a target product profile for a third trimester that someone might receive it out of that window, and so we're interested in the kinetics for those reasons. But really, I think this we're sharing today, we think, is the most important data for our target product profile at this point.

Louis Fries

Yes, this is Louis Fries. I would like to add that some of the data that Greg did not mention but which we we've also seen, as we expected, healthy women have been exposed to RSV before. And so these -- all of these treatment regimens are in fact boosters. And one of the things that was very gratifying to us is that all of the -- virtually everyone was well off, off of their day 0 mark by day 7. There were vigorous responses ongoing even at day 7, which gives us a lot of flexibility. And as we go forward in our trials, we're going to define better the fine kinetics of this antibody response. And that will help us know the optimal time to use it during the third trimester and when we can get the best effect from 1-dose or 2-dose regimens. We -- what we've seen is very gratifying that the early kinetics are quick, which is something we would need to have for this application, and it's there.

George B. Zavoico - MLV & Co LLC, Research Division

So the memory response in these women previously exposed is very robust is what -- basically what you're saying, right?

Louis Fries

Yes, yes, absolutely. The responses are sharp by day 7. They're not nearly as high as they get by day 28, but it's very clear that a strong response is underway as early as day 7.

Stanley C. Erck

And maybe Dr. Piedra can comment on this. But we see in maternal immunization, the vaccine is able to build on some level of immunity that is already effective. It has a limited duration. But this is an added benefit that there's pre-existing immunity, plus we are able to boost on top of that and get very robust immunity. So I think together, that's a -- it's a very feasible place to see the vaccine in the future in the efficacy trial as working well. I don't know, Dr. Piedra, maybe you'd like to comment on this also.

Pedro Piedra

Yes, one other comment. I would agree with all that has been stated. Having a robust early response is definitely crucial. The other aspect that is crucial that will likely be evaluated in future trials is, how much time is required to transfer the antibodies from mother to infant? And that will be very important when one decides what is the optimal timing to vaccinate. From prior studies in pregnant women, we know that we need about a 4-week window from the time of immunization to ensure that there has been sufficient time, one, to induce a robust response and secondly, for that antibody of mothers to transfer to the uterus, so that the uterus or the infant has the maximum amount of antibodies at birth.

George B. Zavoico - MLV & Co LLC, Research Division

A question about manufacturing. I imagine going into the Phase 2B trials, with pregnant women and the repro tox. You're going to need to -- tell me how much you're go to need to scale up. Are you basing [ph] these in reactors, in waves chambers now? Or what do you need to do?

Stanley C. Erck

Yes, George. So that's what we've been doing in parallel with all this work for the past year. And it applies to all of our programs, which is the process development that's required to take -- to bring us from an early stage Phase I and Phase II development company into a Phase III and commercial company. And both were flu, seasonal pandemic RSV, now rabies, we're learning to scale up and develop a late-stage process. All that seems to be coming together now. We're at scales of up to 1,000 liter bioreactors, which we think is commercial scale. So that's where we are.

George B. Zavoico - MLV & Co LLC, Research Division

Okay, terrific. I -- so you mentioned that you're going to be announcing your program going forward in a couple of months. I imagine that also means you'll do that for the seasonal and pandemic, and maybe provide more of a manufacturing update at that time as well.

Stanley C. Erck

Yes, I think in the summer, we'll have -- all the pieces are coming together at the same time, which is convenient and -- for our planning. And the communications will be what -- based with all the clinical data we've had over the past year and currently, plus all the progress we've made in developing a larger scale late-stage manufacturing process. All those will allow us to project the trials that will start later this year and into 2014. And I think we're going to plan a day to -- or a session to discuss that with the public.

Operator

Our next question is a follow-up from the line of Greg Wade from Wedbush.

Gregory R. Wade - Wedbush Securities Inc., Research Division

So with respect to the potential to use 1 or 2 vaccinations, can you just remind us, are any women currently vaccinated twice to try to protect the infant? And with respect to some visibility into the data, could you see a sufficiently robust enough immune response with the -- any of the single-injection vaccinations to give you some confidence that this might be a possibility or the right choice?

Gregory M. Glenn

Hi, Greg. This is Greg. So currently, the pertussis is -- actually, it's a combination of tetanus, diphtheria, pertussis vaccine. It's given once, and that's because it's boosting on top of a pediatric schedule. Often, there's been maybe an adolescent boost. So it's a single dose. And as we discussed earlier, that's a boosting dose, with -- same with seasonal flu. Now seasonal -- and the pertussis vaccine is given in the third trimester. It's aluminum adjuvanted vaccine. The seasonal flu vaccine, as you know, is given at any time in pregnancy, really driven by seasonal -- the season of the -- the flu season. So pre-flu season, they're immunized, and again, that's a single immunization. So that's the current practice for those vaccines. We have, I think, options. We saw very good responses in many of our groups. It's clear that the aluminum adjuvant enhanced that. We got a significant increase at the second dose. But as Lou mentioned, we had a robust response even at day 7 after the first dose. So we're going to lay all those options on the table, look at the different benefits and risks and et cetera, and make a decision later in their clinical development plan. I think we probably will be able to discuss this more in the summer when we can lay out the plans for all of our programs. There is a lot of follow-up, as you probably know. In the U.S., women who are in their last trimester are seen frequently in the clinic. And we think either one of these options certainly would be feasible for implementation. But the data is good enough and gives us several choices. And so we haven't really made a decision based on the data today on our dosing regimen.

Operator

[Operator Instructions] And I see no further questions in the queue at this time.

Stanley C. Erck

Okay. Well, we thank you for your time and attention, and I appreciate your continued interest in our progress. We look forward to bringing you further updates. Okay.

Operator

Ladies and gentlemen, thank you for your participation in today's conference. This does conclude the program, and you may now disconnect. Everyone, have a good day.

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