Ladies and gentlemen, thank you for standing by and welcome to the third quarter 2019 Kura Oncology earnings conference call. At this time, all participant lines are in a listen only mode. After the speaker's presentation, there will be a question and answer session. To ask a question during the session, you will need to press star then one on your telephone. Please be advised that today's conference is being recorded. If you require any further assistance, please press star then zero. I would now like to hand the conference over to your speaker today, Pete De Spain, Vice President Investor Relations at Kura Oncology. Please go ahead.
Thank you, Sarah. Good afternoon, and welcome to Kura Oncology's third quarter 2019 conference call. Joining me on the call from Kura are Dr. Troy Wilson, our President and Chief Executive Officer, and Dr. Marc Grasso, our Chief Financial Officer and Chief Business Officer. Dr. Antonio Gualberto, our Chief Medical Officer and Head of Development, is also with us and available to answer questions. Before I turn the call over to Dr. Wilson, I would like to remind you that today's call will include forward-looking statements based on current expectations. Such statements represent management's judgment as of today and may involve risks and uncertainties that could cause actual results to differ materially from expected results. Please refer to Kura's filings with the SEC, which are available from the SEC or on the Kura Oncology website for information concerning risk factors that could affect the company.
With that, I'll now turn the call over to Dr. Troy Wilson, President and CEO of Kura Oncology.
Thank you, Pete, and thank you all for joining us this afternoon. I'd like to start by introducing the two newest members of our senior leadership team, Kathleen Ford, our Chief Operating Officer, and James Dentzer, our Chief Legal Officer. Kathy joined us in July at a time when strategic prioritization and operational execution became our highest priorities, and she's made an immediate impact. She most recently served at Merck Serono, where she led clinical and development operations towards successful drug registrations in both the U.S. and Europe. Jim joined us just yesterday from Biogen, where he spent the past 13 years, most recently as Senior Vice President Chief Corporation Counsel. He brings a healthy balance of strong business partnering and corporate guardianship, we're excited to have him on board. Both are welcome additions to our team.
Now let me bring you up to speed on each of our programs, beginning with tipifarnib in HRAS-mutant solid tumors. Last week, we reported updated data from our ongoing phase II trial of tipifarnib in HRAS-mutant head and neck squamous cell carcinomas at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, or the triple meeting, in Boston. We were very pleased because the results demonstrate a compelling level of clinical activity for tipifarnib in a difficult-to-treat patient population. They validate our strategy to enrich for clinical activity, and the data strongly support the design of our ongoing AIM-HN registration directed trial. However, before I discuss the significance of these results in more detail, let me quickly recap the data themselves.
As of the October 17th, 2019 data cutoff date, a total of 21 HNSCC patients with high HRAS mutant variant allele frequency were enrolled in the ongoing RUN-HN trial, of whom 18 were evaluable for efficacy. 10 of the 18 efficacy evaluable patients achieved a confirmed partial response for an objective response rate of 56%. In addition, eight patients experienced disease stabilization, including two who achieved an unconfirmed PR, one of whom was awaiting a confirmatory response assessment as of the data cutoff date. The median progression-free survival of the 18 evaluable patients treated with tipifarnib was 6.1 months, compared to 2.8 months on their last prior therapy, including 8.3 months among patients who achieved a PR on tipifarnib and 4.5 months for those patients with stable disease.
Patients had a median of two prior lines of therapy ranging from zero - six, with no responses observed on their last prior therapy. As a reminder, the overall response rates for the three therapies currently approved for the treatment of HNSCC in the second line, pembrolizumab, nivolumab, and cetuximab, range from 13%-16% with progression-free survival of approximately two months. Recall that in our previous update from the RUN-HN trial presented at the European Society for Medical Oncology conference, or ESMO, in October 2018, the data showed a significant association between tumor HRAS mutant allele frequency and clinical benefit from tipifarnib.
We also reported that although the trial was evaluating starting doses between 600 and 900 milligrams BID, our retrospective analysis of patients on study revealed that due to interruptions and discontinuations at the higher dose, the median dose for patients at the end of cycle one was approximately 600 milligrams BID. Based upon these observations, we introduced two changes into the RUN-HN study. First, we require a minimum HRAS mutant variant allele frequency as an entry criterion for enrollment, and second, we established 600 milligrams BID as the starting dose. Notably, we implemented the same changes to the protocol for our AIM-HN registration-directed trial, which was initiated shortly thereafter in November 2018. Since the ESMO 2018 update a year ago, we prospectively enrolled 10 new patients with high HRAS mutant variant allele frequency in the RUN-HN trial.
Of the eight efficacy evaluable patients, three achieved a confirmed PR, five had stable disease, including two patients who achieved an unconfirmed PR, one of whom is pending a confirmatory response assessment. Of the two non-evaluable patients, one discontinued prior to an initial tumor response assessment, the other was awaiting an initial response assessment as of the data cutoff date. With regard to dose, a total of five efficacy evaluable HNSCC patients started at the 600 mg dose in the RUN-HN trial, all of whom achieved an objective clinical response. We believe there are three key takeaways from last week's RUN-HN update. Number one, the requirement of a minimum HRAS mutant variant allele frequency suggests an effective means to enrich for clinical activity in patients with HRAS mutant HNSCC.
Number two, the 600 mg BID starting dose appears to be better tolerated in this patient population and sufficient to drive durable anti-tumor activity. Number three, given that the RUN-HN trial is a multi-center study including more than 30 clinical sites around the world, the data reflect valuable real-world experience with tipifarnib in this clinical setting. Taken together, the results presented at the Triple Meeting reinforce our view that tipifarnib can provide meaningful clinical benefit to HNSCC patients with HRAS mutations, and they further increase our confidence in the design, outcome, and probability of success of AIM-HN, our registration-directed trial of tipifarnib in HRAS-mutant HNSCC. AIM-HN was initiated exactly one year ago and is now open in more than 75 clinical sites in the U.S., Europe, and Asia.
The AIM-HN study is designed to enroll at least 59 evaluable HNSCC patients with high HRAS mutant variant allele frequency who have received prior platinum-based therapy. We continue to believe that the AIM-HN study will take approximately two years for full enrollment. Given the design of the study, there is the potential that the primary efficacy endpoint of AIM-HN could be met if and when 15 confirmed objective responses are observed. It's worth noting that since the introduction of the minimum HRAS mutant allele frequency requirement, we continue to find that approximately 5% of the patients we screen meet the HRAS variant allele frequency requirement for enrollment. Our primary goal for the tipifarnib program is to generate a data package sufficient to support a first application for marketing approval in HRAS mutant HNSCC.
With the compelling signals of activity demonstrated from the Menin MLL data, we're also evaluating how we might pursue opportunities for combination with immune therapy, chemotherapy, and cetuximab in the broader population, including the lower HRAS mutant variant allele frequency population. Given the role of HRAS mutations as a mechanism of resistance to standard therapies, we believe tipifarnib could potentially be expanded to 15%-20% of the HNSCC population, a meaningful commercial opportunity and one in which today there are no direct competitors to tipifarnib. Although we believe combinations in earlier lines of therapy in HNSCC represent immediate opportunities for future label expansion for tipifarnib, we're also laying the groundwork for expansion to other HRAS mutant solid tumor indications. For example, in September, we reported that an investigator-sponsored phase II trial of tipifarnib in HRAS mutant urothelial carcinomas met its primary efficacy endpoint prior to completion of enrollment.
The trial is being conducted at the Samsung Medical Center in Seoul, South Korea. Further analysis of the trial is ongoing, and data are expected to be presented at a future medical meeting. In addition, an investigator-sponsored phase II trial of tipifarnib in lung squamous cell carcinomas continues to enroll patients. The trial is being conducted by a lung cancer consortium that consists of more than 150 public and private oncology centers in Spain. Meanwhile, the discovery of CXCL12 pathway biomarkers offers the potential to expand the opportunity for tipifarnib well beyond HRAS mutant solid tumors.
In June, we showed the first prospective validation of CXCL12 pathway biomarkers to enrich for clinical activity in our ongoing phase II trial of tipifarnib in peripheral T-cell lymphoma, including a 50% complete response rate and a 100% clinical benefit rate in a subset of heavily pretreated patients with angioimmunoblastic T-cell lymphoma or AITL, an aggressive form of T-cell lymphoma often characterized by high levels of CXCL12 expression. We believe the phase II proof of concept data in PTCL-AITL presented at the European Hematology Association Congress and International Conference on Malignant Lymphoma earlier this year support multiple registrational opportunities in relapsed refractory lymphoma, and we continue to gather feedback from key opinion leaders and regulatory authorities around next steps for this program.
Given the high level of clinical activity observed thus far in the AITL cohort, we continue to enroll patients in that cohort in order to acquire more experience regarding safety and tolerability in this patient population. I'm pleased to report that additional data, including new patients from the AITL cohort, have been accepted for an oral presentation by Dr. Thomas Witzig of the Mayo Clinic at the upcoming American Society of Hematology annual meeting in December. Based on our growing body of data, we believe CXCL12 pathway biomarkers may have the potential to unlock the therapeutic value of farnesyltransferase inhibition across multiple hematologic and solid tumor indications, including diffuse large B-cell lymphoma, acute myeloid leukemia, cutaneous T-cell lymphoma, and pancreatic cancer.
Over time, we believe this could enable registrational strategies for tipifarnib in multiple hematologic and solid tumor indications. In further support of our development strategy for tipifarnib, I'm pleased to report that the U.S. Patent and Trademark Office recently issued a new patent, further extending our exclusivity to the use of any farnesyltransferase inhibitor for the treatment of CXCL12-expressing PTCL or AML. This adds to our growing portfolio of patents involving CXCL12 pathway biomarkers. It follows the issuance of another patent this year directed to a method of treating patients with advanced metastatic relapsed or refractory HRAS mutant HNSCC using any farnesyltransferase inhibitor. These new patents expire in 2037 and 2036 respectively, excluding any possible patent term extension.
We believe these new patents strengthen our competitive advantage as we continue to advance the development of tipifarnib, and we intend to continue to aggressively pursue intellectual property protection both in the U.S. and abroad. Let's spend a moment on each of the emerging pipeline programs, beginning with our ERK inhibitor, KO-947. KO-947 is a potent and selective small molecule inhibitor of ERK, which we're advancing as a potential treatment for patients with tumors that have dysregulated activity of the MAPK pathway. Our preclinical data suggest that KO-947 has anti-tumor activity in KRAS or BRAF mutant adenocarcinomas, as well as certain subsets of squamous cell carcinomas. We continue to evaluate dosing regimens for KO-947, including a once-weekly dosing schedule and a more frequent intermittent schedule with a goal of reaching a recommended phase II dose or maximum tolerated dose by the end of this year or early next year.
We were encouraged to see data from an early-stage ERK inhibitor presented at the Triple Meeting last week, including single-agent responses using a similar weekly dosing schedule with intermittent therapy. Although most of the patients enrolled in our study to date have been in more difficult-to-treat populations such as pancreatic and colorectal cancer, the observation of single-agent responses from an ERK inhibitor support our confidence to move forward with KO-947. We continue to believe our phase I strategy will provide a solid foundation to make data-driven decisions on the path forward for KO-947. Our other emerging pipeline program is KO-539, a potent selective small molecule inhibitor of the Menin mixed lineage leukemia, or Menin MLL, protein-protein interaction. Our preclinical data for KO-539 support the potential for potent anti-tumor activity in multiple genetically defined subsets, such as tumors with MLL fusions or rearrangements, as well as NPM1 mutations.
In September, we dosed the first patient in our Phase I clinical trial of KO-539 in patients with relapsed or refractory acute myeloid leukemia, giving us our third wholly owned clinical-stage oncology asset. The Phase I open-label dose escalation study is designed to determine the maximum tolerated dose of KO-539, which will be administered as a once-daily oral dose in 28 continuous day cycles. Upon completion of the dose escalation portion of the trial, expansion cohorts are planned to assess the safety and activity of KO-539 in specific genetic subgroups, such as NPM1 mutants. We believe KO-539 represents a differentiated approach to the treatment of patients with AML, and we look forward to sharing further updates with you. With that, I'll now turn the call over to Marc for a discussion of our financial results for the third quarter of 2019.
Thank you, Troy. Good afternoon, everyone. I'll provide a brief overview of our financial results here on the call and invite you to review our 10-Q file today for a more detailed discussion. Research and development expenses for the third quarter of 2019 were $12.5 million compared to $11.7 million for the third quarter of 2018. The increase in R&D expenses for the quarter was primarily due to an increase in clinical development activities related to our registration-directed trial for tipifarnib. General and administrative expenses for the third quarter of 2019 were $5.1 million, compared to $4.3 million for the third quarter of 2018. The increase in G&A expenses was primarily due to increases in personnel costs and non-cash share-based compensation.
Net loss for the third quarter of 2019 was $16.4 million, or $0.36 per share, compared to $15 million or $0.40 per share for the third quarter of 2018. As of September 30th, 2019, we had cash equivalents, and short-term investments of $250.1 million, compared with $179 million as of December 31st, 2018. Based on our current plans, we continue to believe that our existing cash equivalents, and short-term investments will be sufficient to enable us to fund our operating expenses and capital expenditure requirements into the second half of 2021. With that, I will now turn the call back over to Troy.
Thank you, Marc. Before we jump into Q&A, I'd like to take this opportunity to welcome Diane Parks, the newest member of our board of directors. Diane has held senior commercial roles at leading companies including Genentech, Pharmacyclics, Amgen, and Kite, and she brings valuable experience to our board as we continue to execute on the initial registration-directed trial of tipifarnib and we begin to focus on commercial readiness. With that, operator, we're now ready for questions.
Thank you. As a reminder, to ask a question, you will need to press star then one on your telephone. Our first question comes from the line of Chris Shibutani with Cowen. Your line is now open.
Hey, everyone. This is Pam Barrett on for Chris. I have a couple of questions. The first one is in regard to your biomarker strategy. Should we be expecting at ASH that you'll be breaking down those AITL responses by KRAS3 mutations or other biomarkers?
Pam, thanks for the question. Let me ask Antonio, who's here with us, if he can address your question.
Yes, we are expecting to extend the data that was initially presented at EHA this year. We have continued enrolling AITL patients. We want to further characterize the data with KRAS3 L2. As you may recall, we saw up to 75% response rate. That was quite exciting, and we are fully investigating to determine whether we can sustain this high level of response in the subset of KRAS3 L2 variants.
Got it. Thanks so much. Another logistical question. First, I guess, thanks for the triple meeting data. Congratulations on that. What do you think the enrollment rate will look like compared with that trial in the AIM-HN trial?
Sure, Pam. If you look at RUN-HN and AIM-HN, RUN being the ongoing phase II trial and AIM being the pivotal trial, they're completely different animals, right? RUN-HN is in 30 centers. It's been up and running here for a number of years. AIM is a global registrational directed trial. We're pleased that we're at the point where we have more than 75 sites open. Much of the past year has been spent getting sites online, getting them activated, getting them screening. We're really first in class here, so we're learning as we go. I think we're very pleased with the data coming out of the triple meeting update. It showed that the amendments that we made to the protocol in terms of the variant allele frequency and the 600 milligram starting dose were the right changes.
Now we're just sort of full on in operational execution of the pivotal, and we're still guiding to approximately two years to full enrollment. Hopefully that addresses your question.
Yes. Thank you so much.
Sure.
Thank you. Our next question comes from the line of Reni Benjamin with JMP Securities. Your line is now open.
Hey, good afternoon, guys. Thanks for taking the questions. Congrats on the progress. Troy, maybe just starting off, just based on your discussions with the regulatory agency, I think you mentioned that once the first 15 responders are confirmed, you could potentially go ahead and file. Did I hear that correctly? Is there a minimum duration of response that's necessary for the agency? Can you talk to us a little bit, since we're getting close to this event, a little bit of the commercial strategy that you plan to unfold about how many salespeople do you think might come into the organization and how you plan on moving forward?
Sure, Ren. Thanks for the questions. Let me ask Antonio if he can respond to your question about what happens if and when we reach 15 confirmed objective responses.
Yes. There's no particular requirement by the agency of a specific duration of response. As you can imagine, once you confirm the responses, you will be in Cycle 4 or Cycle 6 in some cases. You already will have seen responses for four to six months. Reminder, the median progression-free survival in this setting is about two months. That gives you an idea. We have also shown progression-free survival recently in our triple meeting update of six months. That gives you an idea of the potential of tipifarnib in this setting compared with the standard of care. As you can imagine, this will be part of the review questions by the FDA. Per se, there's not a particular duration or response requirement for filing in this setting.
Ren, Oh, go ahead. I'm sorry. Go ahead.
No, I was just mentioning that the remaining of the question regarding the commercial strategy.
Yeah. I think as I mentioned, we're quite encouraged by the data that we presented at the triple meeting update. We are beginning the steps for commercial readiness and everything that that entails. I think it's early to be giving you guidance on specifics around an organizational size or structure. We're certainly working through a lot of those details in anticipation of what we hope will be a positive result for the AIM-HN trial here. I would expect that as we get further into it, we'll provide you more guidance on the steps around commercialization. It's just a bit early at this stage, a bit premature.
Got it. Just, you mentioned the potential for combinations and that the triple meeting data really led you to believe this. Can you maybe highlight what within the data is really leading you to this conclusion when these combination studies might in fact begin?
Sure. Again, let me ask Antonio if he can speak to the data and the rationale for the combinations.
Yes. Thank you, Brad. As you have seen from the triple meeting update, the patients carrying HRAS mutations were resistant to the standard of care. It didn't matter if the standard of care or the prior line of therapy was chemotherapy, if it was immune therapy, or if it was cetuximab alone or in combination. In other words, the presence of HRAS mutation drive resistance to the standard of care. When the tumor carries 20% variable frequency of HRAS or higher, you can see activity with tipifarnib as a single agent. The question then remains, when the tumor, let's say, carries 5%- 7%, when does it carry less than 20%?
In those settings, the portion of the tumor with the RAS mutation may not be sufficient for tipifarnib to us as a single agent, but it could be an opportunity for tipifarnib to delay the resistance to the standard of care. This is not just hypothetical. There's actually extensive data in the case of HRAS with cetuximab, so that have been published. They also have been published by Braak and coworkers that when a HRAS mutation is there, normally those patients progress too quickly in the first line setting. Good opportunity for tipifarnib to combine with the standard of care. Maybe an initial approach will be those patients with a low variable frequency of HRAS, but obviously, tipifarnib will have an opportunity to combine with the standard of care eventually in the overall population.
When do you think you might begin those kinds of exploratory studies?
Well, obviously, there's a lot that we have done pre-clinically and we need to make major decisions of what could be the potential combination partners. This is currently that we have the discussion within the company and with others.
Great. Thanks very much.
Yeah, Ren.
Thanks for the questions. Oh, sorry. Go ahead.
Thank you, Ren. Well, I was just going to say on that point, I think now we see sort of two illustrations of our strategy, right? We, as an initial foothold, both with HRAS and now CXCL12, in the context of T-cell lymphoma, we're looking to prioritize those places where we can get accelerated development and ideally approval with a single-arm trial. Looking with an eye toward moving to earlier lines of therapy, moving in combination, and it's important to note, to this point, we don't see any direct competition on either HRAS or CXCL12 from other farnesyltransferase inhibitors. Antonio's right. We're at a point where there's a lot of things we can do with farnesyltransferase inhibition, and we want to make sure we prioritize them and sequence them in the right order, and we'll have more we can share with that in the months to come.
Terrific. Thank you for taking the questions.
Thank you. Our next question comes from the line of Jonathan Chang with SVB Leerink. Your line is now open.
Good afternoon. This is John Barrett on for Jonathan. Thanks for taking my questions. Congrats on having the AITL data being selected for an oral presentation at ASH. If you could you help us set investor expectations ahead of the AITL update in terms of how many more patients and how much more follow-up we might expect versus the data we saw at EHA?
Sure. John, thanks for the question. Let me let Antonio answer your question.
Yeah. I would say that it's just incremental. As you can imagine, the primary endpoint of those cohorts was reached. We have proof of concept both in AITL and the PTCL, NOS. Obviously, we are driven now to the design of the pivotal study, the discussions with the agencies on this design. We want to continue the engagement with investigators and the clinical sites. The study remains open to add additional patients, something very similar to what we did with HRAS. Understand there will be, at some point, a switch from the phase II testing to readiness for a pivotal study.
Got you. Thank you. Regarding those conversations, both internally and with regulators, how are you thinking about a development path forward for AITL and PTCL broadly, and what type of registrational trials you might run?
If you don't mind, Troy will address it. I think the fact that the treatment of tipifarnib with the AITL translated to a high rate or response rate, that opened the opportunity to a potential accelerated approval, or typical conditional accelerated, depending on the agency. Those normally have had designs of single arm, single agent. Similarly towards our HRAS design and strategy. In the case of the rest of peripheral T-cell lymphoma, we saw responses, but we also saw a high rate of disease stabilization that may need a different design, maybe a time to employing, a progression-free survival, et cetera. Basically, what I'm getting to is that it may be required for AITL and AITL-like histologies to follow a single arm approach versus other designs may be required for other subsets of peripheral T-cell lymphoma.
Great. Thank you for taking those questions.
Sure.
Thanks, John.
Thank you. Our next question comes from the line of Tyler Van Buren with Piper Jaffray. Your line is now open.
Hey, guys. Good afternoon. Congrats on all the progress. With respect to the tipifarnib program, clearly you're seeing great data and great response rates in head and neck and AITL on the heme side. In solid, you've got to consider whether you move into earlier lines with combos in head and neck. You've got bladder, potentially lung. In heme, you have CXCL12-positive PTCL NOS, DLBCL. You guys have a lot of potential indications to go after. Can you just take a step back and help us understand, beyond these initial two indications, which one or two might be most interesting to you all and prioritize in terms of moving into late-stage development?
Yeah. Tyler, thanks for the question. Just to confess, it's still a work in progress. I think we're pleased really with two things. One is the level of activity that we're seeing in these biomarker-guided subsets. Maybe three things. The ability to move from the initial relapsed/refractory indications that we can access as a small company to potentially larger indications. Third, as we said in the comments, the growing IP estate that's helping to potentially protect the use of not only tipifarnib, but to exclude others who might come along with farnesyltransferase inhibitors. As Antonio mentioned, we see a clear and compelling opportunity in the head and neck squamous cell carcinoma space.
The level of activity that we're seeing in terms of objective responses is compelling relative to the current standard of care, and there's good rationale to believe that you could move that to earlier lines of therapy, and with thoughtful combinations, that you could broaden the patient population. Those are studies that would likely need, initially, phase I combinations, and then probably larger randomized studies. Those are things that we have to obviously think about carefully, what we would want to take on and the timing. That's clearly an area that we would prioritize. T-cell lymphoma and AITL in particular is just, again, examples where tipi the most active agent.
It gives us a foothold in the heme space, and it gives us an opportunity, as I think you've just articulated, whether we do it alone or whether we do it with a partner, of being able to more meaningfully address some of these larger populations. That question is very much on our mind and something that I think we're going to spend a considerable amount of time going forward trying to get right.
Do you guys expect to have increased clarity on this by, say, the first half or middle of next year? Is that kind of guidance to provide?
Yeah. I understand where you're coming from. We certainly want to be able to provide clarity on next steps, but to the point, some of these studies we can take on now. Some of them are probably better put off to a point where we have greater operational and financial resources, and that's something we'll have to factor in. We expect to be able to give you increasing clarity on the next steps for tipifarnib and our farnesyltransferase inhibitor franchise as we keep going.
Okay, got it. Finally, on KO-539, the Menin MLL inhibitor, can you just briefly describe the dose escalation scheme and whether you think there's the potential to see monotherapy activity and if you guys plan to, and particularly in the subgroups of patients, for example, the patients with fusions, et cetera?
Yeah. Great question, Tyler. Let me ask Antonio if he can answer that for you.
Yes. The design is a modified variation design, but at a high level it is not very different from a three plus three design and maybe with an initial accelerated phase. We are not doing selection in the initial escalations; with that, I'm referring to the NPM1 or the translocation. We reserve our opportunity to select patients when we reach the higher doses. Regarding your initial question, based on the preclinical data, yes, there's an expectation of the probability of responses as a single agent.
Just a quick follow-up. For the patients, the genetic subgroups with MLL fusions or partial tandem duplications or NPM1 mutations, if you combine those, what percentage of the broader population would you say has these genetic classifications?
If we're referring to the adult population, NPM1 will be the major target. It's approximately a quarter of the population. Regarding the other target that you mentioned, the fact is that there's a high level of co-mutations, so it's very difficult to determine what will be a pure population of, let's say, tandem FLT3 versus just NPM1. Most of these patients will have co-mutations, but if we refer to what will be our major target, NPM1, and just base this on public data from TCGA and the like, it's about potentially a quarter of the total population.
Okay. Thanks so much for taking the questions.
Okay.
Thank you, Tyler.
Thank you. Our next question comes from the line of Joel Beatty with Citi. Your line is now open.
Hi, thanks for taking the questions. The first one is maybe a follow-up to a couple other responses earlier in the Q&A, where it seems like there's a lot that Kura is able to take on right now by itself regarding to your pipelining agents. There's also been other opportunities that have been highlighted that may be better handled by a partner. I'm just curious, just thoughts on how to think about the timeline for partnering. Is now a potential timeline where that could be looked at? Are there additional hurdles to get past before that becomes a higher priority?
Yeah. Joel, thanks for the question. Marc's here with me. Let me ask him if he can speak to that.
Sure. Hey, Joel. On partnering, from our standpoint, as we've articulated in the past, doing anything that encumbers rights on tipi, particularly in the U.S., the hurdle there is high for us. We see a very attractive go-it-alone strategy, particularly in the initial markets we're talking about here, including relapsed/refractory head and neck and AITL. I would be cautious to set any timing or expectations around anything we might do on the strategic partnering front, whether it be on tipifarnib or any of the pipeline assets.
Got it. Thanks. Maybe one other question on the HRAS head and neck cancer data. You've demonstrated nicely that higher allele frequency correlates with a higher response rate. Now, my question is, now that that data has been maturing with additional patients over time, have you looked at depth of response and duration of response just to see if there's any correlation on those measures with allele frequency?
Sure, Joel. Let me let Antonio answer that one.
Yeah. That's actually a very nice question. We are noticing some minor differences. Recall that we made some initial distinction last year between the 35% and then the 20%, if we are able to maintain the patient on a study based on performance status, and we are using the albumin of 3.5, and that's surrogate of good performance status. If you look at the data from this year, you can see that out of eight patients that they were in that 20 - 35, four responded versus six responders in the 10 that have higher than 35. Again, small differences, you probably will need more patients, but it still continue the trend, the higher allele frequency you can see better response. The duration response, obviously we'll need a little bit of more time to see any differences between the two.
Last time that I checked personally, I didn't see differences in progression-free survival between those two subsets. In any case, there are good responses in the 20-35 and good responses and activity in higher than 35.
Great. Thank you.
Sure.
Thanks, Joel.
Thank you. Our next question comes from the line of Jay Olson with Oppenheimer. Your line is now open.
Oh, hi. Thanks for taking the question, and congratulations on the data at the triple meeting last week. According to our interviews, it seems like physicians were favorably impressed by the data you presented last week. I was wondering if you could please share with us some of the feedback you received from oncologists attending that meeting, and whether or not you think that data might potentially accelerate the enrollment rate in your AIM-HN study.
Thanks, Jay, for the question, and let me let Antonio speak to your question.
Yes. I have to say that we have received very positive feedback, not just from the physicians attending the meeting, but also the members of our trial sitting committee. As you can imagine, many of the authors were also European authors. There's actually much excitement for the confirmation of the strategy, the activity of the 600 milligram dose, and the application of the variable frequency. We agree with you that we expect this will potentially increase, or we believe will increase, the testing or further testing of patients with head and neck through next-generation sequencing, and that increase in the testing will translate to higher enrollment of eligible patients.
Okay, great. Thank you. Maybe if I could just ask one follow-up. As you contemplate moving tipifarnib into combination studies for head and neck squamous cell carcinoma, what is the HRAS mutant allele frequency cutoff that you would use in those combination studies? Would it be the same that you're using in monotherapy, or would it be different?
I'll address it also. It's actually a very good question, and they are both clinical rationale, but also technical rationale. Currently, since the higher than 20% allele frequency is optimal population for activity as a single agent, we also will continue pursuing tipifarnib monotherapy in that 5% of the population using current technologies, both of the NGS testing in tissue, but also we have available plasma assays that we can develop. We can identify perhaps another 20% of the patient. As you can imagine, that limit is a technological limit. You can potentially expand that population going lower than 1%, perhaps 0.5%. There's a possibility of expansion of the population based on the lower limit of detection of these assays, and we have a number of partners that are perfectly capable to identify that population.
Currently, we are giving that number of perhaps 20% of head and neck because we feel fairly confident of the assays that we have in hand. The NGS technology improves every year and there could be potentially, if anything, an increase of the potential target population.
Okay, great. Thank you for taking the questions, and congrats again on the progress.
Thank you.
Thanks, Jay.
Thank you. As a reminder, to ask a question, you will need to press star then one on your telephone. Our next question comes from the line of Joseph Pantginis with H.C. Wainwright. Your line is now open.
Hi, guys. This is Pasquale Sansone from the line of Joe. Congrats on the update on RUN-HN trial. I have just a question on RUN-HN. Basically, by analyzing tipifarnib PFS curves based on prior therapies, it looks like the tipifarnib shows a greater PFS in CPI failures. After checkpoint inhibitors. Could this data suggest a potential rationale of combining a CPI to tipifarnib in order to increase durability of response? Can you please comment on this?
Sure. Thanks for the question. Let me let Antonio take that one.
Just to be clear, this may require more patients, but we currently do not see differences based on the prior use of immunotherapy versus prior use of cetuximab. I think the good news is that with the progression of the immunotherapy to the first-line, if anything, further validate the use of tipifarnib in second-line as monotherapy. That said, I agree with your point that the presence of even lower allele frequency HRAS mutation in the front-line, that most likely will translate to the appearance of progressions on the use of immunotherapy along in combination with chemotherapy in the front-line. There could be an opportunity of potential regimens of chemotherapy, immunotherapy plus tipifarnib. We mentioned initially maybe a high-risk subset could be those patients that could, for example, be tested in plasma for the presence of circulating HRAS.
That could be a population that we are estimating of about 20% of the patients. As I said previously, that subset can potentially increase depending on the technological advantages of the use of NGS.
All right. Thank you so much. Also a follow-up question. You said that you are studying different combination treatments in preclinical models. Are you seeing more activity when you combine tipifarnib with an immunotherapeutics or not?
Yeah. You can anticipate that we are going in that direction, but we currently have not released that data. As you can imagine, yes, we are doing those experiments at the current time.
All right. Thank you so much and congrats on the progress.
Thank you.
Thank you.
Thank you. This concludes today's question and answer session. I would now like to turn the call over to Troy Wilson for closing remarks.
Thank you, Sarah. Thank you all for the questions and for participating in our call today. Before we conclude, let me just quickly lay out our anticipated milestones over the next 12 months. For tipifarnib, additional phase II data in AITL at the ASH meeting in December, regulatory feedback from our phase II trial in AITL in the first half of 2020, additional phase II data in chronic myelomonocytic leukemia or CMML in the first half of 2020, additional phase II data in urothelial carcinoma in 2020, initiation of a proof of concept study in pancreatic cancer in 2020, and potential for full enrollment of AIM-HN by the end of 2020. For KO-947, our ERK inhibitor, completion of the dose escalation portion of the phase I trial by the end of 2019 or early 2020, and initiation of one or more tumor-specific extension cohorts in 2020.
For KO-539, achievement of a recommended phase II dose in 2020. We're planning to be at the Stifel Healthcare Conference in N.Y. in two weeks, and we look forward to seeing many of you there. In the meantime, if you have any additional questions, please feel free to contact Pete, Marc, or myself. Thank you again, and have a good evening, everyone.
Ladies and gentlemen, this concludes today's conference call. Thank you for participating. You may now disconnect.