Kristin Hodous - IR Jeff Albers - CEO Mike Landsittel - VP, Finance Andy Boral - CMO.

Eric Schmidt - Cowen and Company Cameron Bradshaw - Goldman Sachs Chris Raymond - Raymond James Mike King - JMP Securities David Nierengarten - Wedbush Securities Carmen Augustine - Jefferies Arlinda Lee - Canaccord.

Good morning. My name is James and I will be your conference operator today. At this time, I would like to welcome everyone to Blueprint Medicines First Quarter 2017 Financial and Operating Results Conference Call. All lines have been placed on mute to prevent any background noise.

After the speakers' remarks, there will be a question-and-answer session. [Operator Instructions]. Thank you. Kristin Hodous, you may begin your conference..

Thank you, Operator. Good morning. This is Kristin Hodous of Blueprint Medicines and welcome to Blueprint Medicines first quarter 2017 financial and operating results conference call. This morning we issued a press release which outlines the topics that we plan to discuss today.

The release is available on the Investor Section of our website at www.blueprintmedicines.com.

Today on our call, Jeff Albers, Chief Executive Officer, will discuss Blueprint Medicines' first quarter 2017 business highlights and review our recent clinical updates; and Mike Landsittel, Vice President of Finance, will review our first quarter financial results. We will then open the call for your questions.

Andy Boral, our Chief Medical Officer, will also be available for Q&A. Before we get started, I would like to remind everyone that statements we make on this conference call will include forward-looking statements.

Actual events or results could differ materially from those expressed or implied by any forward-looking statements as a result of various risks, uncertainties, and other factors including those set forth in the Risk Factors section of our most recent Annual Report on Form 10-K filed with the SEC and any other filings that we may make with the SEC.

In addition, any forward-looking statements made on this call represent our views only as of today, and should not be relied upon as representing our views as of any subsequent dates. We specifically disclaim any obligations to update or revise any forward-looking statements. Now, here is our CEO, Jeff Albers..

Thanks, Kristin, and good morning everyone. 2017 has been a busy year for Blueprint Medicine so far and I'm happy to share recent progress as we work to build a broad pipeline of transformative medicines for patients with cancer and other rare diseases.

In the first quarter, we continue to advance our two lead therapeutic candidates BLU-285 and BLU-554 in the clinic.

In addition with the initiation of a Phase 1 trial of BLU-667 in RET ultra cancers we now have three wholly-owned therapeutic candidates in the clinic with the potential to address at least six distinct patient populations with significant medical needs. We also recently raised $215 million in the successful follow-on offering in April.

The proceeds further strengthen our balance sheet and enable us to expand and accelerate our clinical program. All of these activities contribute to the four areas of focus for 2017 that I introduced on our last call.

Our first area of focus for the year is to progress our Phase 1 clinical trial of BLU-285 and BLU-554 towards key data disclosures later this year.

Today we're pleased to announce that the first of these updates will come on June 5 at the 2017 ASCO Annual Meeting where we will present updated data during an oral session from our BLU-285 trial in patients with gastrointestinal stromal tumors or GIST.

In the first quarter, we announced that we initiated the expansion phase of the study and therefore the data at ASCO will include results from the entire dose escalation portion of the trial, including safety, data, and assessments of clinical activity, as well as early safety and clinical data from the dose expansion portion of the trial for a subset of patients with sufficient follow-up.

As we disclosed earlier this year it's our intention to create a natural cadence of data disclosures at major medical conferences over the course of the year. To this extent, we expect to provide updated data from our ongoing trials of BLU-554 in Hepatocellular Carcinoma and BLU-285 in Advanced Systemic Mastocytosis by year-end.

In April, we delivered three oral presentations on the discovery and preclinical development of BLU-285 and BLU-554 at the ACR Annual Meeting and at the American and Chemical Society Meeting. While both therapeutic candidates emerged from our discovery processes they came from two different avenues.

BLU-285 was a direct hit from our proprietary compound library and BLU-554 came from our rational design approach. Once the initial scaffolds were identified we then refined both compounds through extensive medicinal chemistry work.

All together these presentations offered us an opportunity to reflect on the power of the Blueprint Medicines platform and our tremendous progress over the last six years.

We're extremely proud of how far we've come and the rapid achievement of clinical proven concept for these programs and believe it's a testament to the commitment and capabilities of our scientists.

Directly related to the continued clinical progress our second area of focus for 2017 is to further define the long-term clinical and regulatory path for BLU-285 and BLU-554.

Across the two BLU-285 studies and the BLU-554 studies we're actively evaluating a range of options for expedited developments based on the encouraging preliminary data sets we've reported last year. As mentioned on prior calls, additional clinical data over the course of this year will help us to define the path for each program.

Today, however I want to highlight our efforts to advance BLU-285 inject. Currently we're in the process of seeking feedback from regulatory authorities to help us evaluate options for potential expedited development in PDGFR alpha-driven GIST and KIT-driven GIST two distinct patient population.

In the PDGFRalpha Group preliminary data showed strong clinical activity for BLU-285 at all dose levels. We believe these results may enable an expedited path to approval in this population based on expansion of the ongoing single arm trial.

In the KIT Group BLU-285 showed evidence of clinical activity at higher dose levels thus indicating the potential dose response. These results are encouraging because patients were generally heavily pretreated and enrolled with highly refractory disease.

Additional data from the ongoing expansion part of the trial will inform the optimal registration strategy which we believe could include either an expedited path or as discussed on our last earnings call moving from the ongoing study directly into a randomized Phase 3 trial.

To prepare for either scenario we're moving forward with plans to initiate a randomized Phase 3 trial which could serve as a confirmatory or initial registration trial depending on the chosen approval path.

We expect the trial to run in parallel with the ongoing Phase 1 expansion potentially offering an opportunity to incrementally reduce the time differential between the two scenarios. Currently we're actively exploring trial design options with clinical experts and we look forward to updating you on our plans in the coming months.

Our third area of focus is to continue to focus on maximizing the value of our scientific platform. We're proud of our diverse and growing pipeline which we believe is differentiated for a company of our age and size.

However the true power of the platform and the opportunity it offers to consistently advance innovative compounds into our development pipeline comes with a responsibility to carefully manage the portfolio.

We regularly evaluate the scientific and financial rigor of each program and opportunity with a goal of making efficient and well informed go, no go decision. In fact, as we often note, we've hosted more programs at Blueprint Medicine and we progress through this disciplined portfolio management process.

The output then is that we believe we've advanced the most exciting programs into the clinic and this now includes our newest therapeutically candidate BLU-667. BLU-667 is particularly promising just because it was specifically designed to not only target reputations and fusion, but it also addresses predicted resistance mutations.

This will finally offer patients more profound and durable responses over the long-term. Earlier this year, the first patient was dosed with BLU-667 in a Phase 1 trial that includes patients with non-small cell lung cancer, medullary thyroid cancer and other solid tumors with a RET alteration.

The initiation of this trial achieved an important 2017 goal and we look forward to sharing data next year. Finally our fourth strategic priority is business development which we also view as a key portfolio management tool. We continue to actively evaluate a range of collaboration opportunities across the pipeline.

Given our strong financial position, we'll only explore such collaborations if we believe the partner will allow our program to exceed our internal threshold of additional speed and geographic reach.

To that end, our emphasis is on identifying partners who can help us move one of our more advanced therapeutic candidates more quickly towards approval and into the hands of patients and physicians worldwide.

Together our continued focus on these four areas creates the potential for an eventful year and we're off to a strong start with one initiation of our BLU-667 clinical study, two the acceptance of our data from the BLU-285 GIST study for an oral presentation at ASCO, and three a successful financing that affords us flexibility to execute against our plan.

We anticipate a range of additional important milestones in 2017 including new data from each of our BLU-285 and BLU-554 clinical program along with updates on our clinical and regulatory plans. Now I'm going to turn it over to Mike Landsittel to review our financial results for the quarter..

Thanks, Jeff. Blueprint Medicine continues to operate from a very strong financial position. As Jeff mentioned the end of the first quarter was highlighted by our successful follow-on offerings which closed in early April.

The offering resulted in net proceeds of approximately $215 million which will enable us to continue to expand our clinical development activities for our lead programs. As of March 31, 2017, we had cash, cash equivalents, and investments totaling $236.3 million as compared to $268.2 million as of December 31, 2016.

Our cash, cash equivalents, and investments, as of March 31 exclude the net proceeds from our follow-on offerings which we received in April. After giving effect to the offering, we would have had cash of approximately $450 million as of March 31.

Based on our current plans, we expected our cash, cash equivalents, and investments, including the net proceeds received from the April offerings but excluding any potential option fees and milestone payments under our existing collaborations will be sufficient to enable us to fund our operating expenses and capital expenditure requirements into the second half of 2019.

Importantly, we believe this will allow us to reach numerous potential data readouts and inflection points across our portfolio. Turning now to our P&L. Collaboration revenues were $5.8 million for the first quarter of 2017 compared to $6.8 million for the first quarter of 2016.

This decrease was primarily due to the recognition of a milestone in the first quarter of 2016 as well as lower reimbursable R&D expenses in our collaboration with Alexion based on the timing of certain R&D activities.

Research and development expenses were $28.5 million for the first quarter of 2017 compared to $17.6 million for the same period in the prior year.

The increase in R&D spending was primarily driven by increased clinical and manufacturing expenses associated with advancing our ongoing clinical trials as well as increased personnel related expenses which includes stock-based compensation expense.

G&A expenses were $5.6 million for the first quarter of 2017 compared to $4.6 million for the first quarter of 2016. The increase in G&A spending is primarily due to increased personnel related expenses which again also includes stock-based compensation expense.

Net loss for the first quarter was $28 million or $0.84 per share compared to a net loss of $15.5 million or $0.57 per share for the same period in the prior year. As we have highlighted on the call, we continue to be very excited about the opportunities ahead of us in 2017, and believe that we are well positioned financially to execute on our goal.

With that, we would now like to open up the call for your questions.

Operator?.

[Operator Instructions]. Your first question comes from the line of Eric Schmidt from Cowen and Company. Go ahead please. Your line is open..

Good morning, thanks for taking my call and congrats Blueprint team on the progress. Jeff, it sounds like you're having some productive early discussions with the FDA and other regulators around 285 and GIST.

What do you need on your end to bring those discussions to conclusion? Do you think you have enough data from the Phase 1 and early expansion cohort studies or are you still waiting for more data either in PDGFR or c-KIT driven GIST?.

Thanks, Eric. So we always think about it when you say to a conclusion, we always think about our dialogue with regulatory agencies as a continuum and it's an ongoing discussion and so nothing in our hands today changes that.

As we noted, we think the data we shared particularly around the PDGFRalpha subset was particularly compelling and as we've guided to previously, we would seek to have a face-to-face meeting over the first half of this year.

What we haven't said or what is strictly our practices that when we have that type of feedback we will look to find forum to share the specific feedback. So we're not at that point yet but we certainly would be looking to do provide an update very soon..

Okay.

And may be in terms of the upcoming ASCO presentation, I guess can Andy tell us roughly how many more patients we might see and you do the two GIST cohorts at ASCO?.

It's Andy, Eric. I will -- so thanks for the question. So the study continues to enroll, enroll well and we are adding sites to prepare for the expansion parts, we are continuing to expansion process I should say. But we really do want to keep the whole dataset intact and presented at once at ASCO and Dr.

Heinrich will present the current update of the enrolment as well as the latest anti-tumor activity and safety data both on the escalation part of the study and on the expansion part of the study for patients who have sufficient follow-up..

I think we saw 36 patients at EORTC and 28 of them were valuable Andy is it going to be meaningfully more than that?.

Yes we continue to enroll at a similar pace. So I think it'll be -- it'll be enough -- it will be enough more than that to have a more complete story to tell..

The way I think about that as a matter of course we'll take the same approach this year with all of our data updates that we did last year which is we obviously have a certain amount of data when we submit the abstract but we'll look to do a data cut closer to the time of the conference to include as much data, additional data as possible when we share that at the time..

Your next question comes from the line of Terence Flynn from Goldman Sachs. Go ahead please. Your line is open..

Hi. This is Cameron on for Terence. Thanks for taking our question. May be just one on BLU-285 for SM. Can you provide any update on the expansion portion of the trial, can you tell us what dose or doses will be explored and then how many patients are you targeting for enrolment? Thank you..

This is Andy, I will take that. So the ongoing Phase 1 study in mastocytosis is on track and as we said in the release, we expect to initiate the expansion part of the study soon. We have now dosed up to the MTD defined in the GIST study, we don't plan to go higher than that.

However we still -- we're still evaluating the top dose level to determine the actual specific recommended dose for the part two -- for part two of the study.

The study design is as outlined in the clinical trial.gov and in the expansion part we have three groups the aggressive mastocytosis, the aggressive with actually the advanced mastocytosis advanced with another heme disorder and mast cell leukemia. And that part of the study includes about 35 patients..

Your next question comes from the line of Chris Raymond from Raymond James. Go ahead please. Your line is open..

Great. Thanks. So another question on BLU-285 in SM, so maybe around the midostaurin approval, so this drug, the label, and the data are focused on advanced SM. You guys have indicated an interest in exploring indolent disease and I think some of the data that we have seen with midostaurin is that there is a tolerability issue for sure.

May be just talk about the different risk-benefit profiles that you see between indolent and advanced SM and how you see BLU-285 fitting into both -- now that this drug is on the market and may be if you can give any feedback in terms of enrollment dynamics since that approval and your view there. Thanks..

Thanks, it's Andy. I will take that. So I want to start by saying that it's really gratifying to us to see that a new medicine approved for patients with advanced systemic mastocytosis, obviously there is a huge need there.

That being said, we do think that 285 offers a unique selective approach to mastocytosis therapy and that is distinct from the approach taken by Midostaurin. In terms of -- in terms of the indolent aspects of the disease we -- as we disclosed at the ASH Meeting where Dr.

Angelo presented at the ASH Meeting at the end of last year, we were very encouraged to see evidence of activity at the earliest dose levels with a very well tolerated safety profile and that is what really gives us a lot of -- has really expanded our interest in a broader range of population -- broader population mastocytosis including the indolent population.

We are working now with clinical experts. We will have Advisory Meeting in the coming months and we will be planning interactions with health authorities really to design right clinical trials to evaluate BLU-285 in indolent and with mastocytosis patients.

Regarding potential impact or potential or I guess the potential now, the approval just occurred but Midostaurin are in enrolment of our study. Now we don't really expect to see much impact. Midostaurin has been available through compassionate use throughout the entire period that our study was running.

We see patients who have and have not had prior Midostaurin on the study already. So I don't -- we don't expect to have any meaningful impact on the conduct of the ongoing study..

Your next question comes from the line of Mike King from JMP Securities. Go ahead please. Your line is open..

Hi good morning guys, thanks for taking the question. Just wanted to follow-up with questions on 285 and 544 for that matter.

I'm just generally maybe missed it, but have you stated whether you have reached MTD on either? And specifically on 285, I'm wondering if we should think about MTD being different or driven by, maybe that's a better way to put it, driven by coverage of the various KIT mutations in GIST?.

Mike its Andy, I will take that. So I'll start with 285, so yes we have disclosed that we determine the MTD and the recommended dose for BLU-285 in GIST, that's 400 milligrams once a day and the expansion part of that study is ongoing.

As you know, as Eric Evans presented at ACR when you will see biochemical assay BLU-285 has potential to inhibitor broad range of activating mutations and resistance mutations in kids and this raises the possibility that we might have activated across a broader GIST population perhaps in earlier lines of therapy.

But I think it's important to keep in mind there's always a lot of uncertainty, when we translate preclinical data to patients.

So we are encouraged by the emerging clinical and safety data we have that we're seeing in but we need to complete the expansion part of the study to really understand the breadth of activity across the range of the KIT driven GIST population..

Okay.

Do you feel comfortable you've got tolerability to go above 400 milligrams?.

We have already determined that the doses we explored above 400 milligrams [indiscernible] --.

Okay..

So we won't go above 400 milligrams. And you also had asked about 554. So in 554 we actually did present the or disclose the maximum tolerated dose late last year and that's 600 milligrams once a day and that we're expanding in that in the HCC expansion cohorts at that dose level.

We are still looking at the biomarker positive I see FGF19 positive subset and amplify positive subset on the completing a negative subset -- biomarker negative subset..

And may be just -- go ahead, Jeff..

To add one additional point there is that we did amend both the HCC trial design and the GIST trial design to allow for a higher number of patients in both of those studies as we moved into the expansion phase..

Right. Okay. I know you have talked about in heavily relapsed or heavily treated GIST that you might do a randomized study against imatinib rechallenge.

I don't know if you can give any more color on that, if that's still a part of your thinking on that?.

Yes, it's Andy. So Mike our initial plans for Phase 3 development, first I should really say we are working them, we have had recently had advisory meetings here at Blueprint to talk to some of the key leaders in the GIST community.

As Jeff mentioned, we're planning regulatory interactions with both the FDA and European Health Authorities really to map out the most efficient path forward -- regulatory path forward in GIST.

As I think we've discussed before I think our big -- our initial Phase 3 just really focuses on moving into earlier lines of therapy such as potentially a head-to-head versus regorafenib and then third line GIST translated other possibilities in later disease.

And I think it's the outcome of our advisory meetings and our regulatory interactions will really help us to find the most appropriate path forward..

Okay. All right.

Then just speaking of earlier lines, on the PDGFRalpha population, I'm just trying to envision what kind of agent you could randomize against if you were to do a randomized study in treatment-naive PDGFRalpha patients or would they have to at least have failed imatinib before rolling to 285?.

So in PDGFRalpha we remain very encouraged by the preliminary data that we've seen and included the data we presented at the end of last year and we do think that that is a situation where there is a very real opportunity for the accelerated approval based on and in expanded set of single agent, single arm data, and that is a path we will discuss with regulatory authorities.

If that results -- if we are successful there and achieve an accelerated approval, I think there are variety of possibilities for a confirmatory study and those are issues we'll discuss with the regulators.

But it doesn't necessarily have to be a randomized study just in PDGFRalpha patients there I think -- I think that would be obviously a tough study to do when we have to think about variety of different options..

Your next question comes from the line of David Nierengarten from Wedbush Securities. Go ahead please. Your line is open..

Hey thanks for taking the question. I just had one on 554. We saw at AACR a FGF401 response rate in liver cancer being 8% PR and 52% stable disease, 4.1 median duration.

Is that kind of the benchmark to be looking for 554 when you report out the next set of results? Do you think you need to beat that level or duration of response? How you are thinking about the competitive space there? Thanks..

Thanks, David. Yes, this is Andy, I will take that.

So we were very pleased with the very -- the very preliminary data that we presented at the Triple Meeting at the end of last year, where we -- was primarily data from the escalation part of the study at that point, we did have I think the key things we found that we're very encouraged by that we clearly demonstrated that BLU-554 has preferential activity in the biomarker positive meaning FGF19 positive subset of patients with tumor shrinkage in five out of 10 patients at that point in time and that certainly give us enthusiasm to continue the study.

In terms of the potential approval pathways for 554 in HCC, we certainly plan to evaluate opportunities for expedited development based on additional data from the ongoing Phase 1 trial and which will primarily now be expanded data from the -- at the maximum tolerated dose and the recommended dose that we're expanding at now.

But I think it's really premature to comment on what the specific parameters would be for an expedited approval pathway. In general, we do see HCC as a classic opportunity for expedited approval the patients have a very poor prognosis even with the available therapies and I don't think that's really changed even with the approval of sorafenib.

But in terms of the specifics that will be the outcome of discussions with regulatory authorities..

And then maybe just a quick follow-up on the -- just back to what we saw with FGF401. They saw some responses in both FGF19 negative and positive patients.

Your selectivity is just better I mean and you are more likely to see the responses in the overexpressed patients or is there any other profile -- product profile differences that you are thinking about?.

Yes. So that was very interesting to see the FGF401 data at -- we just recently in April I guess it was. We are very convinced from our data that FGF -- that BLU-554 is preferentially active in the biomarker positive population as we defined PDGFR for pathway activation measured by FGF19 or expression using chemistry.

And as I mentioned we did see tumor shrinkage in five to 10 biomarker positive patients using those criteria. Novartis is using a completely different method to select patients it's RNA-based and the resulting population is almost certainly different. So it makes it pretty hard to compare results between the two..

Got it. Thanks. Just checking..

[Operator Instructions]. And your next question comes from the line of Carmen Augustine from Jefferies. Go ahead please. Your line is open..

Hi guys, thanks for taking the question.

So for BLU-667 in lung cancer with RET fusion, could you speak a bit to the competitive landscape and how you see 667 potentially being differentiated from other kinase inhibitors that have activity against KIT -- I'm sorry RET?.

This is Andy, I will take that. Thanks very much. So we really think BLU-667 is a very special inhibitor of RET, it's been I mean it's pretty impressive chemistry feat.

We designed a compound that is a very potent and selective inhibitor of the wild type RET kinase which is the kinase infusion, that predominates in lung cancer, colon cancer and a variety of other small fraction, variety of other tumors.

It also varies selectively inhibits the activating mutations that predominate in medullary thyroid cancer and it was also designed to hit some of the key predicted resistance mutations that based on our date and others we would expect to primary causes of resistance when patients are treated with the non-selective RET inhibitors out there that are currently available and in use.

And at the same time it was particularly designed not to inhibit a variety of other targets that we think are responsible for lot of the toxicities of the non-selective compounds used inhibitor RET such as VEGF receptor.

And so we think that combination really makes it completely different from the available multi-kinase therapies out there cabozantinib and vandetanib, some of the other broad compounds used to treat -- used to treat lung cancer now and we look forward to testing it in the clinic and proven that clinically..

Great, thanks. And then, in SM, you mentioned additional results would be available later in 2017 and I think you have mentioned in the past that would include response rate data.

So would there be response data available from both the escalation and expansion cohorts later this year?.

Are you talking about BLU-667?.

No, SM..

SM, I'm sorry BLU-285 and SM.

Yes so we do plan to update the ongoing study later this year and I would anticipate that would include data but certainly from the escalation part of the study and similar to the approach we're taking with BLU-285 and GIST, we would update with data from patients with sufficient follow-up in the expansion part of the study..

Your next question comes from the line of Arlinda Lee from Canaccord. Go ahead please. Your line is open..

Hi guys, thanks for taking my questions. A couple of questions on 285.

Can you remind us how many -- I'm sorry -- on the data that we're going to see at ASH, we will see the complete data set for the dose escalation portion of the trial, is that correct?.

This is Andy, I will take that. So BLU-285 in GIST we are talking about right yes.

So we will present the complete data from the escalation part of the study with the understanding that patients continue on study we don't have a defined endpoint but we will present the data supporting the choice of the MTD and recommended dose and we will have substantially more information on both anti-tumor activity and safety in that population.

So that will essentially complete that escalation dataset and we will as I think Jeff had mentioned we will also present preliminary data from expansion part of the study on patients who had a sufficient follow-up..

And then how many -- sorry in the dose-escalation portion, how many patients are at that 400 milligram dose that you have decided to use for the expansion cohort?.

So again I would really like to leave the details for Dr. Heinrich to present. So he will give all the numbers of patients length of follow-up et cetera but we would rather not getting to that in pieces here..

Okay.

And then on the randomized Phase 2 that you are planning, can you clarify, is that going to be just for KIT or what are you guys thinking at this point, second line versus third line, only KIT, kit and PDGFR?.

In terms of GIST, yes so we haven't really talked specifically about our randomized Phase 2 study. I think what we have said at this point is that we're really excited based on the data we have in hand we are very excited to get moving get a Phase 3 study in earlier line of therapy started sooner for two reasons.

One it may be necessary the confirmatory study following if we successfully achieve and accelerated approval in the PDGFRalpha subset of GIST.

And it would all -- it may also serve as an initial approval study in GIST depending on the status of PDGFRalpha of course would give us potential the opportunity to get into the broader range of KIT driven patients.

At the moment, I was saying earlier we are most interested now looking at third line GIST compared to regorafenib but we are also considering other possibilities and we will discuss that further with our clinical advisors and regulatory authorities..

May be Arlinda I will just add one commentary from a simplistic perspective way, I think about that is there are two paths forward.

What we have done in the first quarter once we hit the recommended Part D doses we amended the protocol both in the PDGFRalpha arm and the KIT driven arm such that we maintained the potential based on the results we see in those subsets to move forward on an expedited path.

In the meantime if either of those are successful we would knew and know that we have to have a confirmatory study and what we've tried to do is more aggressively move forward with that study because in essence it creates a hedge for us that is either the confirmatory study or if we decide that we need more data and there is not an expedited path for either of the two arms that could then become our registration path.

And what we need to close that loop is regulatory feedback one, and then, additional data from the expansion arms two, and we will then make that decision later this year..

Okay. Great. And then on the expansion trial of 55 -- or a portion of the trial for 554, you had initially talked about having three different groups.

Are you going to enroll equally into each of these three groups or is there a possibility to enroll more in the high FGF19 group?.

Arlinda, this is Andy. I'll take that one up. So we are enrolling all three excuse me, expansion groups the IHC positive, the amplified, FGF19 amplified and the biomarker negative group.

And we have recently -- we've -- this is I think should be a couple of trials though, we have recently expanded the IHC positive so overexpressed group of patients in that study from 15 to 30 because we think that's based on our data that we presented earlier or at the end of last year we think that the group where we have the most opportunity to see activity..

Okay.

And then I guess just given some of the other data that was presented at AACR, I know you talked a little bit about the competitive landscape and how it might not be apples to oranges, but can you may be talk about, I guess, the emerging landscape with other drugs targeting FGF in HCC and what do you think the bogeys might be or what information do you need to get to those decisions?.

So I think the -- it's Andy again. The only compound that's with really clinical data that's been presented now is FGF19 from Novartis and I think it was. It looks, looks like an interesting compound. As I was saying earlier they've taken a very different approach to patient selection and it makes it very hard to compare our results to theirs.

We're very confident that our IC based FGF19 is identifying a pathway activated population. And again we think our data demonstrates that if you have excuse me 554 is preferentially active in that population. I think that's using a different approach there. Jeff are one day is likely in a different population.

Really though I think the answer is that overtime we just need to see how the clinical data evolved in the clinical trials. And so we're pretty much focused on executing our study understanding how our compound behaves in the amplified patients in the overstressed patients and mapping out the most appropriate path to registration for BLU-554.

And I think that's really we're going to -- where we're going to focus more than worrying too much about the other compounds..

[Operator Instructions]. And your next question comes from the line of Mike King from JMP Securities. Go ahead please. Your line is open..

Hey guys. Thanks for taking the follow-up. I was just wondering if, on 667, if we have any further color or you are attempting to get more detail on the epidemiology of RET? I believe RET is part of the Foundation Medicine panel, but maybe I'm wrong.

I am just trying to get a sense of the prevalence of either RET mutations; RET translocations in the broad solid tumor population..

Mike, it's Andy. So I'll starting that and so it is, so RET is covered by the Foundation Medicine panel that's and I think that is one of the -- that will be over time one of the sources of patients who are known to be RET activated.

We based on current data we think that it's in the range of 1% to 2% of non-small cell lung cancer patients and the large majority I think Medullary thyroid cancer patients, it is a -- its RET is the drivers in the congenital syndrome that are associated with Medullary thyroid cancer.

It's also identified I think fusions more than limitation as an activator in a smaller fraction of a very broad range of solid tumors. I've seen reports of ranges from I don't know 0.1% to 0.5% something like that.

And I think it's very -- I think that’s really uncertain at this point time it'll, it'll require data a lot more data from folks like Foundation Medicine who are screening large numbers of patients really answer that question..

Mike, maybe I'll add one piece to that, this is Jeff.

With all of our programs when we're going after a targeted patient population I think it's suffice to say that our understanding of the underlying data is always evolving that is trying to get the best available handle on the number of patients if you take systematic massive psychosis that's one for instance where there isn't a great data set our source to look to.

And one of the ways we -- we practically address that is how is our ability to identify these patients in our trials.

And one of the things that we found gratifying to-date is that in all four of our trials we've been able to work with investigators who seem to have those patients and have them in numbers that allow us to enroll each expansion phase or escalation phase quickly and then as we've moved into expansion phase we've seen that accelerate in the two cases where we're now into expansion.

So well that's not a specific number if I apply that to the RET study we started that as all Phase 1 is in the first cohort where we only had one site up and running and now with each subsequent cohort we're adding sites and find it easier to identify those patients. So RET is fitting the mould of our prior therapies quite nicely thus far..

Okay. And stupid question, but I would imagine most of these -- are these naive patients or I imagine most patients will be treated with cabozantinib.

It's Andy. In terms of our study we're pretty early and so we don't have a very good understanding of will enroll but across the -- across the field of RET active enough non-small cell lung cancer. Actually [indiscernible] based chemotherapy is still standard of care and that would be I would expect that all our patients will have received that.

I guess we'll see in terms of the other multi targeted inhibitors as we talk to our investigators they're not very enthusiastic and those drugs like cabozantinib..

And there are no further questions at this time. I'd like to turn the call back over to you Mr. Albers..

Thanks, Operator. We're looking -- as we look out over the rest of the year with continued enthusiasm especially with regard to our ongoing clinical trials as we just walked through in some detail during the Q&A.

And on behalf of more than a hundred employees at Blueprint Medicine we want to thank all of you for your support interest in the company and we look forward to providing updates with you all again soon. Thanks for your time and have a great day. Bye..

This concludes today's conference call. You may now disconnect..