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ImmunoGen (NASDAQ:IMGN)
Q4 2018 Earnings Conference Call
Feb. 8, 2019 8:00 a.m. ET

Contents:

  • Prepared Remarks
  • Questions and Answers
  • Call Participants

Prepared Remarks:

Operator

Good day, and welcome to the ImmunoGen fourth-quarter 2018 and year-end results conference call. Today's conference is being recorded. At this time, I would like to turn the call over to Ms. Courtney O'Konek.

Please go ahead.

Courtney O'Konek -- Director, Corporate Corporations

Good morning, and thank you for joining today's call. Earlier today, we issued a press release that includes a summary of our recent progress and fourth-quarter and full-year 2018 operating results. This press release and a recording of this call can be found under the Investors and Media section of our website at immunogen.com. On the call today are Mark Enyedy, our president and CEO; and Anna Berkenblit, our chief medical officer.

Rich Gregory, our chief scientific officer; Blaine McKee, our chief business officer; and Dave Foster, our chief accounting officer, will join the team for Q&A. During today's call, we will highlight key accomplishments with the business over the last 12 months, review our fourth-quarter and year-end financial reports and discuss upcoming milestones. During the discussion, we will use forward-looking statements, and our actual results may differ materially from such statements. Descriptions of the risks and uncertainties associated with an investment in ImmunoGen are included in our SEC filings.

And with that, I'll turn the call over to Mark.

Mark Enyedy -- President and Chief Executive Officer

Thanks, Courtney. Good morning, everyone, and thank you for joining us today. 2018 was another year of rapid execution and significant progress for ImmunoGen, led by the completion of enrollment in Forward 1, our registration study for mirvetuximab in platinum-resistant ovarian cancer, the presentation of combination data and over 100 patients to support label expansion for this program, and the advancement of our earlier-stage portfolio. With the benefit of this performance, we entered 2019 poised to deliver on a number of important catalysts, including top-line results from Forward 1 in the first half of the year, potential BLA and MAA submissions for mirvetuximab monotherapy in the second half of the year, additional data from combination studies with mirvetuximab and from expansion studies in AML and BPDCN for our programs targeting hematological malignancies, and filing an IND for our next development program, IMGC936, before the end of the year.

We also come into the year with a strong balance sheet and a proven management team that brings deep experience in oncology development and commercialization to deliver on the business. This combination of assets and capabilities positions us well to execute on our strategy and generate significant value in the coming year. As a reminder, we've set four strategic priorities for the company: first, complete the development and launch mirvetuximab in 2020 for the treatment of women with platinum-resistant ovarian cancer; second, accelerate our IGN programs in hematological malignancies; next, build upon our leadership position in ADCs through continued platform innovation; and finally, expand the reach of that innovation and maintain financial strength through high-value partnerships. Over the last 12 months, we've made significant progress toward each of these objectives.

For mirvetuximab, we successfully completed a prespecified interim futility analysis for Forward 1 and finished patient enrollment in this study in April, well ahead of schedule. We believe this rapid approval reflects the oncology community's interest in mirvetuximab and underscores the need for new treatments for this disease. In June, the FDA granted fast-track designation for the program. And as the year progressed, we advanced our precommercial and launch-readiness activities for mirvetuximab.

To date, we've completed a thorough assessment of the market opportunity for mirvetuximab in ovarian cancer with the goal of building a preliminary go-to-market model. We validated commercial drug product, which is now in inventory, initiated the PMA submission for a folate receptor alpha companion diagnostic and began a staged approach to building out our commercial team. On the strength of this execution, we're on track to report top-line data from Forward 1 in the first half of the year. With positive data, we would expect to submit a BLA and an MAA for full approval of mirvetuximab, a single-agent therapy, for the treatment of women with platinum-resistant ovarian cancer in the second half of the year.

In addition to the monotherapy indication, we continue to advance our Forward 2 study to expand the benefit of mirvetuximab into earlier treatment settings for ovarian cancer. Over the course of 2018, we presented data of more than 100 patients from our Forward 2 study of mirvetuximab in combination doublets with Keytruda, Avastin and carboplatin in women with platinum-resistant or platinum-sensitive ovarian cancer. We also completed patient enrollment in the triplet combination cohort evaluating mirvetuximab plus carboplatin and Avastin. Looking beyond mirvetuximab, our novel IGN programs 632 and 779 have demonstrated encouraging early results in hematological malignancies, which were presented at ASH in December.

Our early stage pipeline has also yielded our next promising development candidate IMGC936, a first-in-class ADAM9-targeting ADC, which is being developed in collaboration with MacroGenics. We plan to file the IND for the 936 before the end of the year. Together with our platform, each of these assets has the potential to create significant additional value for ImmunoGen. We also achieved a number of operational milestones over the last year, including an upsized and oversubscribed secondary that raised $163 million of net proceeds in June and, most recently, the sale of our residual rights to receive royalties on commercial sales of Kadcyla for $65 million.

Through these transactions, we start 2019 with approximately $325 million on our balance sheet. With respect to the remainder of our financial results, this morning's press release covers the detail. So briefly, we generated $54 million in revenue over the course of the year. Operating expenses for the full year were approximately $214 million, of which $174 million was in R&D expenses, driven by mirvetuximab and 632 clinical trial costs and precommercial activities for mirvetuximab, most notably manufacturing.

For 2019 financial guidance, we expect cash and cash equivalents at December 31, 2019, to be between $135 million and $140 million, revenues to be between $40 million and $45 million and operating expenses between $265 million and $270 million. We anticipate that current cash, combined with the cash receipts expected from partners and collaborators, will enable us to fund our operations at least a year beyond the release of top-line results from the phase three Forward 1 trial, which, as I mentioned, is expected in the first half of 2019. With that, I'll turn the call over to Anna to review our pipeline progress. Anna?

Anna Berkenblit -- Chief Medical Officer

Thanks, Mark. As mentioned, 2018 was another year of significant progress toward our highest-priority objective, which is to bring mirvetuximab to market as monotherapy for women with platinum-resistant ovarian cancer in 2020. Our Forward 1 study is progressing well. The pivotal phase three trial was designed to enroll 333 patients with folate receptor alpha-positive platinum-resistant ovarian cancer, who have received up to three prior treatment regimens.

The study randomize patients two to one to receive mirvetuximab or physician's choice of liposomal doxorubicin, weekly paclitaxel or topotecan. The primary endpoint is progression-free survival, or PFS, by blinded independent central review in the entire study population, which includes both medium and high folate receptor alpha expressors, as well as in the subset of patients with high folate receptor alpha expression. Based on the encouraging and consistent safety and activity observed in clinical studies to date, we believe that mirvetuximab has the potential to displace chemotherapy as a single-agent treatment in the platinum-resistant setting. And we look forward to assessing the top-line data in the coming months, with a plan to present the data at a medical meeting later this year.

In addition to mirvetuximab monotherapy, we're advancing the combination expansion cohorts in the Forward 2 trial looking at mirvetuximab in combination with Avastin or Keytruda in patients with folate receptor alpha-positive platinum-resistant ovarian cancer, as well as the triplet combination cohort that is evaluating mirvetuximab plus carboplatin and Avastin in patients with recurrent platinum-sensitive disease. As Mark mentioned earlier, over the course of 2018, we reported data on more than 100 ovarian cancer patients treated with mirvetuximab in combination with either Avastin or Keytruda. We have established that full-dose mirvetuximab can be combined safely with full doses of Avastin, Keytruda and carboplatin with no new safety signals. And we have reported encouraging initial antitumor activity across the doublet combination cohorts.

In the fourth quarter, we completed enrollment of 41 patients in the triplet cohort ahead of schedule. In addition, based on the encouraging data reported to date with mirvetuximab in combination with Avastin, we initiated a second mirvetuximab plus Avastin cohort in a patient population that we're calling platinum agnostic. These are patients who may or may not meet the criterion of platinum resistance, that is, recurring within six months of their last platinum, but they are, nevertheless, appropriate candidates for a nonplatinum-containing doublet, such as mirvetuximab plus Avastin. We expect to enroll approximately 40 to 60 patients to generate additional data to guide label expansion for this combination doublet.

As Forward 2 continues, our goal remains to establish mirvetuximab as the combination agent of choice in ovarian cancer and to support its use in earlier lines of ovarian cancer therapy. To this end, we plan to present initial data from the triplet cohort, as well as mature doublet expansion cohort data at medical meetings over the course of 2019. Moving to our novel IGN programs, IMGN632 and IMGN779 are being investigated in hematological malignancies with a focus on AML and BPDCN. Despite several new treatment approvals for AML in recent years, a significant need remains for these patients.

Last year, both of these programs were granted orphan drug designation from the FDA for the treatment of AML. Our new IGN payloads, which are DNA-acting agents, are designed to overcome the limitations of first-generation cross-linking agents of this class. Our IGN payloads find just one stranded DNA, retaining potent antitumor activity while sparing normal healthy cells, which, we believe, will facilitate repeat dosing and prolongs time on treatment. In December at ASH, we reported encouraging phase one data on both IGN programs in back-to-back oral presentations.

IMGN632 is a CD123-targeting ADC that deploys our most potent IGN payload. Initial data from the phase one study of 632 in patients with relapsed or refractory AML and BPDCN showed that IMGN632 displays antileukemia activity across all dose levels tested and a tolerable safety profile at doses up to 0.3 milligrams per kilogram. Enrollment in expansion cohorts is ongoing to identify the recommended phase one dosing schedule, so that we can move forward with IMGN632 monotherapy development in BPDCN, as well as additional combination studies in AML, which we plan to initiate this year. IMGN779 is our CD33-targeting ADC, which again displays quite favorable tolerability with repeat dosing across a range of doses in relapsed AML.

Encouragingly, in data presented at ASH, we saw antileukemia activity in more than 40% of relapsed/refractory patients. This year, we expect to establish the recommended phase one dosing schedule for IMGN779 to move forward within combination regimens in AML. As we look ahead, we have several important clinical milestones in 2019, with most notably the top-line Forward 1 data in the coming months. Now I'll turn the call back over to Mark.

Mark Enyedy -- President and Chief Executive Officer

Thanks, Anna. Coming back to the business today, we generated significant momentum across ImmunoGen in 2018 and entered 2019 from a position of strength, with important near-term catalysts with our lead program, our earlier-stage portfolio accelerating and an experienced management team to deliver on our commitment to bring more good days to people living with cancer. We look forward to another exciting and productive year, and we'll update you on our progress in the coming months. With that, we'll open the line for questions. 

Questions and Answers:

Operator

[Operator instructions] We will now take our first question from John Newman of Canaccord.

Please go ahead. Your line is now open.

John Newman -- Canaccord Genuity -- Analyst

Hey, guys, good morning. Thanks very much for taking the question. So Mark and Anna, back last year in October, we saw some interesting data for mirvetuximab in combination with pembrolizumab at ESMO. And I'm wondering, since that time, have you seen any maturation of that data? I recall when those data were initially presented, you had told us that the PFS data, especially, were a bit immature.

So I'm just curious if maybe you've seen any signs since then that those data continue to mature.

Anna Berkenblit -- Chief Medical Officer

John, we continued to follow the patients on that cohort, but our attention, really, in terms of data cleaning and focus right now is on the Forward 1 phase three trial. So we are following patients on mirvetuximab and pembrolizumab as the data mature and look forward to presenting it later this year.

John Newman -- Canaccord Genuity -- Analyst

Great. And a follow-up question for you, Anna. I think you previously said that it seems to be that the proportion of patients for each choice in the control arm, paclitaxel, liposomal doxorubicin and topotecan, I think you've previously said that, that is pretty reflective of what you see in the real world. Is that the case?

Anna Berkenblit -- Chief Medical Officer

Yes. That's the case. So we buy data from real-world use. And typically, what we see is the majority of patients with platinum-resistant ovarian cancer receive pegylated liposomal doxorubicin, primarily because it's a pretty convenient schedule, and it's given once a month.

The next most common is weekly paclitaxel. Physicians typically give that for patients who've had a good response to every three-week paclitaxel and they've recovered from neuropathy. And then topotecan is also approved and used.

John Newman -- Canaccord Genuity -- Analyst

Excellent. All right. Great. Thanks very much, guys.

Operator

We will now take our next question from Michael Schmidt of Guggenheim. Please go ahead.

Michael Schmidt -- Guggenheim Securities -- Analyst

Hey, thanks for taking my question. I had another one regarding the Forward 1 trial. And I know you've done a lot of work previously in terms of dosing and ocular prophylaxis. And we've heard from docs that mirvetuximab is considered very well tolerated so far.

And so I was just wondering in this context maybe what assumptions you have incorporated in the Forward 1 trial with respect to potential dropouts or dropout rate.

Anna Berkenblit -- Chief Medical Officer

So there were two factors that we took into consideration when we made assumptions about the dropout rate. One is, as you point out, Michael, the potential for patients, if not well managed, to drop out because of ocular adverse events on mirvetuximab. And the other was potentially for patients on the control arm to drop out once they realize that they were randomized to the control arm because it is an open-label study. And so we put a lot of effort into educating investigators and making sure we had patient-facing materials for the ocular profile to minimize the dropout rate.

And the dropout rate that we've seen across the study is consistent with our expectations.

Michael Schmidt -- Guggenheim Securities -- Analyst

OK. Helpful. And I guess, just to play devil's advocate, should the Forward 1 study fail, I guess, to what degree might or might not affect your plans to starting mirvetuximab in combination with the mentioned drugs, including Avastin or carboplatin going forward?

Anna Berkenblit -- Chief Medical Officer

So it really would depend on why the study fails, Michael. There are many scenarios that one could contemplate where the study is not statistically significantly positive for the primary endpoint. And so we would really need to understand the monotherapy data that would really drive our next steps for development for mirvetuximab from a registration perspective, either it's monotherapy or it's combination.

Michael Schmidt -- Guggenheim Securities -- Analyst

Makes sense. And then the last question, one housekeeping question around your operating expense guidance. I was just wondering if that is a cash figure or that includes noncash comp and then what assumptions you have baked into that guidance with regards to mirvetuximab commercialization activity.

David Foster -- Vice President Finance, Chief Accounting Officer

This is David. Those -- that guidance includes both cash and noncash operating expenses. That's directly from expected P&L for next year. So stock comp would be in there.

Michael Schmidt -- Guggenheim Securities -- Analyst

OK. And then does that include a initial build-out of the commercial infrastructure? Or maybe a more substantial build-out? Or is that still pending on the data itself?

David Foster -- Vice President Finance, Chief Accounting Officer

Yes. So it does include the build-out of the commercial organization. So we're assuming success with respect to that guidance. And it's a staged approach, Michael.

So right now, we're managing all of our precommercial planning with existing headcounts, but the goal would be benefit of a positive readout to begin -- build in with a significant amount of that expense coming in the back half of the year.

Michael Schmidt -- Guggenheim Securities -- Analyst

Right. Thank you so much.

Operator

We will now take our next question from Jessica Fye of JPMorgan.

Jessica Fye -- J.P. Morgan -- Analyst

Hey, guys. Good morning, and thanks for taking my questions. Couple on Forward 1. If we think about the enrollment of that trial, can you ballpark how much of that enrollment occurred toward the end of the study, say, in the last three months that you're enrolling patients? Second, can you confirm if you have hit the target number of PFS events yet, I think, in response to the first question? And you might have said your focus is now cleaning data for Forward 1.

Does that imply that the full number of events has been hit? And third, can you remind me if OS is relevant from a regulatory standpoint at all here. I.e. if OS data starts to mature while the filing is under review, has the FDA provided feedback on how they would interpret that information?

Anna Berkenblit -- Chief Medical Officer

Thanks, Jess. So you may recall last year that we completed enrollment ahead of schedule, nearly two months ahead of schedule. And so enrollment was brisk over the last three months of the trial. I can't quote you exactly what percent of patients were enrolled then.

But again, toward the end, enrollment was quite brisk. Regarding your second question, we are focused on data cleaning as we have been for many months now, so that we can get the trial over the finish line, so to speak. But my statements were not intended to imply anything regarding whether or not we have hit the target number of events. And then as to your third question, regarding overall survival, it is a key secondary endpoint.

The study is not powered to show a statistically significant improvement in overall survival. However, we would expect that all of the endpoints are consistent, and so we'd expect to see a trend in overall survival in the right direction. And typically, we would anticipate providing updated overall survival data to FDA with the Day 120 update.

Jessica Fye -- J.P. Morgan -- Analyst

Great. Thank you.

Operator

We will now take our next question from Biren Armen of Jefferies Bank. Please go ahead.

Biren Amin -- Jefferies Bank -- Analyst

Yes. Thanks for taking my questions. Just to clarify on the prior question and response, Anna. What would trigger cleaning of the trial? Would it not be triggered by achievement of the final event? Or are there other parameters that you would consider?

Anna Berkenblit -- Chief Medical Officer

We clean data throughout the course of the trial. And again, there was no trigger to start data cleaning. Data cleaning started as soon as we started enrolling patients in the trial. But again, as one reaches toward the end of the trial, there is an increased focus on that.

And all I can say is, for the past many months now, we have been focused on cleaning the data.

Mark Enyedy -- President and Chief Executive Officer

Yes. Biren, this is Mark. I mean, just keep in mind, the minute you have your first screen failure, you start to collect data and try and lock down these patients. And then as the study is clean and moves forward, patients come off study.

The goal is to clean and lock down as many of those patients as you can before you get to your final event. And so as Anna was saying, obviously, the more patients we recruit, the higher the volume of that activity. So that's all that was implied by that statement.

Biren Amin -- Jefferies Bank -- Analyst

Got it. And then I guess, given the Forward 1 trial design on PFS endpoint on both the overall cohort and the high FR expressors, let's just say, if the overall cohort misses, what type of a PFS manifest would you need to see in the high FR expressors to hit a p-value of 0.025 or less?

Anna Berkenblit -- Chief Medical Officer

There are different scenarios for that, Biren. So I don't think I can give you an exact answer because there are different scenarios. But overall, what I can tell you is, we have designed the study looking for PFS improvement from three and a half a months in the control arm to six months in the experimental arm, which translates into a hazard ratio of 0.58. And we're going to be looking for that delta, if you will, both in the ITT and the high subset.

And if we miss on the ITT, we can still claim success in the high subset.

Biren Amin -- Jefferies Bank -- Analyst

OK. And then maybe just one more question on Forward 1. Given the chemotherapy arm allows for investigator's choice of three chemo agents, how should we think about the distribution of each of those three agents in the trial? And do you expect any geographic differences between U.S. versus ex U.S.

sites in terms of choice of chemo agent?

Anna Berkenblit -- Chief Medical Officer

So as I mentioned, we anticipated that the distribution of investigator choice chemo in the trial would reflect real-world usage. And in the real world, as we discussed, Doxil tends to be used most often followed by weekly paclitaxel and topotecan. And given what we know about usage in the U.S. and Europe, we do not anticipate differences in those two geographic regions regarding preferences for each of these single-agent chemotherapies.

The practice is pretty similar with regard to choice of single-agent chemotherapy.

Operator

We will now take our next question from Debjit Chattopadhyay. Please go ahead.

Debjit Chattopadhyay -- Janney Montgomery Scott -- Analyst

Hey, good morning, and thank you for taking the questions. So I'm going to stay away from Forward 1, but maybe a two-part question on the Keytruda combo. So first, maybe in the platinum-resistant setting, would you pursue the Keytruda combo or stick with agents with established activity in the platinum-resistant setting? And then secondly, in the platinum-sensitive patients, would you not think that the Keytruda/carboplatin/mirv would make the most sense given the lessons from non-small cell?

Anna Berkenblit -- Chief Medical Officer

Thanks, Debjit. So for platinum-resistant ovarian cancer, which is where we initially explored mirvetuximab plus pembrolizumab in our still following patients, it's going to really depend on how the data look when we do look at it in terms of maturity. And so we haven't made a decision yet there. Regarding platinum-sensitive ovarian cancer, I agree with you that the data that pembrolizumab has generated with platinum-based therapy for non-small cell lung cancer is really quite nice and could potentially be relevant in the ovarian cancer setting.

And at the moment, however, we're focused on following patients on our triplet with carboplatin, mirvetuximab and Avastin. But I agree with you that pembrolizumab-based triplet is something we could consider in the future.

Debjit Chattopadhyay -- Janney Montgomery Scott -- Analyst

And then the three chemos that are being used, obviously, there is kind of a spread of outcomes for the individual chemos. But more recently, weekly paclitaxel seems to be doing better in terms of outcomes, but Doxil is most commonly used. Any thoughts on that dichotomy there? Or people are yet to catch up with weekly versus what was previously approved?

Anna Berkenblit -- Chief Medical Officer

So I think, typically, ovarian cancer patients wind up getting multiple lines of therapy. And the sequencing of single-agent chemotherapy in the platinum-resistant setting is really based on physician-patient conversations around what is important to the patient in terms of the adverse event profile, the schedule, etc. I will remind everyone that we are stratifying patients in our trial on several characteristics, including selection of single-agent chemotherapy. So that is one of the stratification factors, Doxil, topotecan or paclitaxel.

And the other stratification factor is one to two versus three prior therapies. So whatever factors physicians take into consideration when they assign the investigator-choice chemotherapy, we'll make sure that it's stratified so there's balance across the arm.

Mark Enyedy -- President and Chief Executive Officer

I mean, part of this is, typically, a platinum-sensitive patient is going to get a platinum-based doublet that usually has taxane as its partner. And so once you've gotten to a platinum-resistant patient, rather than reintroduce taxane with peripheral neuropathy and the other thing, the fall is more likely to be liposomal doxorubicin. And that's, in fact, what we see in the marketplace today, both here in the U.S. and in Europe.

And in fact, single-agent chemotherapy has a higher percentage of usage in the platinum-resistant settings, about 80% of patients in the EU versus about 60% here. Is that helpful?

Debjit Chattopadhyay -- Janney Montgomery Scott -- Analyst

Yes. Keeping fingers crossed. Good luck.

Operator

We will now take our next question from Andy C. of William Blair. Please go ahead.

Unknown Analyst

Thanks for taking my question. So I have one. Curious to hear Anna's take on this recent negative trial, JAVELIN Ovarian 200. It's a triple arm study, right, avelumab plus Doxil versus avelumab versus Doxil.

So I think the Doxil arm, actually, underperformed versus historical norms. And just curious your view on that and its potential relevance to your control arm assumptions for Forward 1.

Anna Berkenblit -- Chief Medical Officer

So I am aware that they have press released top-line data from JAVELIN 200, where they described response rate and hazard ratios. But I don't believe that I have seen the absolute value for progression-free survival for any of the arms. So I really can't comment on that, but I guess, what I would say for that study is, it has not achieved proof of concept for checkpoint inhibitors in platinum-resistant ovarian cancer. And I would also point out that the JAVELIN, I think, it was 100, the ovarian trial in the frontline setting was also stopped early at interim analysis for futility.

Operator

We will now take our next question from Boris Peaker of Cowen. Please go ahead.

Boris Peaker -- Cowen and Company -- Analyst

Thanks for squeezing me in. Maybe on Forward 1, and we talked about a lot of the incremental details as you're working to finish up the study. But I'm just curious, do you think the data is going to come in 1Q or 2Q?

David Foster -- Vice President Finance, Chief Accounting Officer

Yes. Boris, thanks. We haven't narrowed the guidance. So what we've said previously and where we are today is that we expect this study to read out in the first half of the year.

Boris Peaker -- Cowen and Company -- Analyst

Gotcha. OK. And maybe on the combos, obviously, you've done a lot of work on the combos and a lot of the data keeps maturing. But what is the strategic plans on actually starting a pivotal study for any of the mirvetuximab combos?

Anna Berkenblit -- Chief Medical Officer

So we have two options at the moment for combination studies that we're thinking about moving into the next registration study: one is mirvetuximab plus Avastin; and one is the triplet of carboplatin, mirvetuximab plus Avastin. And we continue to gather data for both of those regiments to help inform our next decision regarding our next registration trial. So for mirvetuximab plus Avastin, we are actively enrolling our second cohort, which we call the platinum-agnostic cohort, and we plan to enroll between 40 and 60 patients there to see consistency of data, we hope, with the initial cohort that we have published, and also the triplet, which we have completed enrollment ahead of schedule in December last year, and we look forward to initial safety data from that this year and then, subsequently, efficacy data. Now remember, the triplet cohort, these are platinum-sensitive patients, and so it will take a while before we have mature data from not just an ORR but PFS perspective for decision-making.

Boris Peaker -- Cowen and Company -- Analyst

Gotcha. And my last question on 779. I'm just curious what the development strategy there is? And would you have to do a head to head against Mylotarg at some point? Or can you avoid doing that?

Anna Berkenblit -- Chief Medical Officer

So for 779, you may recall that we've demonstrated quite nice favorability and, definitely, antileukemia activity. And in discussions with investigators, there is interest in continuing development of IMGN779 as a combination therapy. So the first thing would be for us to figure out really what the recommended phase one dosing schedule is for 779 for -- to proceed in combinations. At this point, we do not have plans to do a head-to-head monotherapy versus Mylotarg.

Boris Peaker -- Cowen and Company -- Analyst

Thank you very much.

Operator

We will now take our next question from Jonathan Chang of SVB Leerink. Please go ahead.

Jonathan Chang -- SVB Leerink -- Analyst

Hey, guys. Thanks for taking my questions. Couple of questions. One on Forward 1.

Can you talk about the reasons for confidence and how the control arms expected to perform? And then second question, can you talk about your expectations for how many of the patients on Forward 1 with the FR alpha high?

Anna Berkenblit -- Chief Medical Officer

Sure. So in terms of our confidence in the control arm, all I can say is that it has increased since when we started the study and we designed it. We designed it really benchmarking the control arm on the Aurelia study, where the control arm, which included the same drugs that we're including, had a median progression-free survival of 3.4 months. So that was our foundational assumption.

And then in the fall last year, the CORAIL study read out, and that was over 400-patient study in platinum-resistant disease, not just with one to two priors like Aurelia, but one to three priors like ours. So I think it's the best benchmark out there and the most recent benchmark out there. And there, the control arm contained two of the three drugs that we're including in our phase three trial, and again, the median PFS there was 3.6 months. So we're confident in the performance of the control arm.

In terms of your second question regarding how many patients will be folate receptor alpha high, what we have typically seen throughout the development program is that about 40% of ovarian -- of epithelial ovarian cancer is about high, 20% medium, 20% low and 20% negative. And that's -- so we anticipate that the majority of patients will be eligible for mirvetuximab based on medium or high expression. And again, we anticipate that the majority of the patients in the trial will be high based on the distribution that we've seen thus far.

Operator

[Operator instructions] We will now take our next question from Kennen MacKay of RBC Capital Markets. Please go ahead.

Kennen MacKay -- RBC Capital Markets -- Analyst

Thanks for taking my question and thanks for being so candid in elaborating on this. And I have another one for you. It's actually a four-parter here. First, I just wanted to confirm that in Forward 1, there are no platinum-refractory patients.

And then I had just wanted to double-check on how the chemotherapy protocols are sort of defined -- the options are defined in Forward 1, whether this is actually restricted to current label usage or site protocol usage or NCCN guideline usage or anything along those lines. Third, I just wanted to double-check the definition of number of prior therapies in Forward 1 and see if this referred to total lines of therapy, including combo therapies or whether this referred to the number of prior therapies, for instance, with carboplatin plus paclitaxel plus Avastin be considered a single-line or three priors? And then lastly, I just wanted to see if the arms were at all balanced for platinum-free interval or prior response to therapy or duration of response.

Anna Berkenblit -- Chief Medical Officer

All right. So first -- no, this is great, Kennen. Super. Good questions here.

So the first one, we have excluded primary platinum-refractory disease. That is a small subset of ovarian cancer patients who just, basically, blow through their initial therapy and progress on their initial platinum-based doublet. They typically do poorly, no matter what. However, we are allowing patients with secondary platinum-refractory disease.

So what I mean by that is that they -- after their, like, second line of therapy, they may have progressed on that. But again, we've excluded primary platinum refractory only. Regarding your second question, the dosing schedule of the chemotherapies that we used in our study are those that investigators actually use. They're not necessarily the labeled dose.

So a good example of that would be Doxil. The label dose is 50 milligrams per meter squared, and that's tough for patients to tolerate due to mucositis, hand-foot syndrome. So we're using the more commonly used regimen of 40 milligrams per meter squared. And similarly, for topotecan, we're allowing 1.25 milligrams per meter squared daily times five, which is a bit less than approved dose of 1.5.

And we're also allowing the weekly regimen for topotecan, given some studies showing similar activity and potentially better tolerability. So we're using the doses that investigators typically use in the clinic. Regarding your third question, we are referring -- when we say number of priors, we really mean lines of therapy. So Taxol-carbo-Avastin with Avastin outback as maintenance would be considered one line of therapy.

And then regarding your last question, whether or not the arms are balanced for platinum-free interval or response to prior therapy, that is not a specific stratification factor. We already had plenty of stratification factors with folate receptor alpha, number of priors and choice of investigator chemotherapy. But given the size of the study, we hope that random chance will allow for balance for that factor as well as what other -- whatever other factors are maybe important.

Kennen MacKay -- RBC Capital Markets -- Analyst

Awesome. And maybe just one quick follow-up on the lines of therapy. Does that include neoadjuvant and adjuvant? Or is that just for metastatic disease?

Anna Berkenblit -- Chief Medical Officer

Yes. Neoadjuvant and adjuvant are considered one line of therapy.Thank you very much.

Operator

It appears at this time, there are no further questions. I would like to turn the conference back to Mr. Mark Enyedy.

Mark Enyedy -- President and Chief Executive Officer

Great. Thank you, operator. We apologize for the audio challenges that we had to start the call this morning. I appreciate your patience, and we look forward to keeping you updated on our progress as we move through the remainder of the first half of the year.

Thanks very much.

Operator

[Operator signoff]

Duration: 42 minutes

Call Participants:

Courtney O'Konek -- Director, Corporate Corporations

Mark Enyedy -- President and Chief Executive Officer

Anna Berkenblit -- Chief Medical Officer

John Newman -- Canaccord Genuity -- Analyst

Michael Schmidt -- Guggenheim Securities -- Analyst

David Foster -- Vice President Finance, Chief Accounting Officer

Jessica Fye -- J.P. Morgan -- Analyst

Biren Amin -- Jefferies Bank -- Analyst

Debjit Chattopadhyay -- Janney Montgomery Scott -- Analyst

Boris Peaker -- Cowen and Company -- Analyst

Jonathan Chang -- SVB Leerink -- Analyst

Kennen MacKay -- RBC Capital Markets -- Analyst

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