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Karyopharm Therapeutics Inc (NASDAQ:KPTI)
Q1 2021 Earnings Call
May 3, 2021, 8:30 a.m. ET

Contents:

  • Prepared Remarks
  • Questions and Answers
  • Call Participants

Prepared Remarks:

Operator

Good morning. My name is Jason, and I'll be your conference operator today. At this time, I would like to welcome everyone to the Karyopharm Therapeutics' First Quarter 2021 Financial Results Conference Call. There will be a question-and-answer session to follow. Please be advised that this call is being recorded at the Company's request.

I would now like to turn the call over to Mr. Ian Karp, Karyopharm's Senior Vice President, Investor and Public Relations.

Ian Karp -- Senior Vice President, Investor and Public Relations

Great, thank you. And thank you all for joining us on today's conference call to discuss Karyopharm's first quarter financial results and business update. And let me be the first one to officially welcome our new President and Chief Executive Officer, Mr. Richard Paulson, to our quarterly earnings call. This is Ian Karp and today, in addition to both Michael Kauffman and Richard Paulson, I'm also joined by Mr. Mike Mason, our Chief Financial Officer; Mr. John Demaree, Chief Commercial Officer; and Mr. Stephen Mitchener, our Chief Business Officer.

On the call today, Michael will provide an overview of key recent corporate developments and an update on our commercial progress, followed by an update on one of our key pipeline opportunities in endometrial cancer. Mike Mason will then provide an overview of the first quarter financial results. We will conclude with some thoughts from Richard on Karyopharm's future, and then we will move to the Q&A portion of the call.

Earlier this morning, we issued a press release detailing Karyopharm's results for the first quarter of 2021 and the appointment of Richard Paulson as our next President and CEO. These releases along with a slide presentation that we plan to reference on today's call are available on our website at karyopharm.com.

Before we begin our formal statements, I'll remind you that various remarks we make today constitute forward-looking statements for purposes of the safe harbor provisions under the Private Securities Litigation Reform Act of 1995 and as outlined on Slide number 3. These include statements about our future expectations, clinical development, regulatory matters and timelines; the potential success of our products and product candidates, including our expectations related to the commercialization of XPOVIO and NEXPOVIO; financial projections and our plans and prospects.

Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including those discussed in the risk factors section of our most recent Annual Report on Form 10-K, which is on file with the SEC and in other filings we may make with the SEC in the future. Any forward-looking statements represent our views as of today only. And while we may elect to update these forward-looking statements at some point in the future, we specifically disclaim any obligation to do so even if our views change. Therefore, you should not rely on these forward-looking statements as representing our views as of any date subsequent to today.

I'll now turn the call over to Dr. Michael Kauffman, Co-Founder of Karyopharm and our first CEO, and now please turn to Slide number 4.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Thank you, Ian, and good morning, everyone. Let me begin first by saying how thrilled I am to also be joined here today with Richard Paulson, our Company's new CEO, and we'll begin on Slide 4.

When Dr. Sharon Shacham and I started Karyopharm over 12 years ago, our mission was really quite simple, we wanted to do everything we possibly could to make a difference in the lives of patients battling cancer. More specifically, we sought to develop novel drugs that exploded a fundamental pillar of oncogenesis, namely the reactivation of tumor suppressor proteins by inhibiting their export out of the cell nucleus, which as you may know is actually where the name Karyopharm comes from.

Now with our lead medicine XPOVIO, having received three separate FDA approvals and one marketing authorization in Europe, over 450 employees and a robust pipeline of programs across both hematologic and solid tumor indications, I could not be more proud of the work we've accomplished on behalf of patients, their families and healthcare providers. But as our Company is increasingly focused on commercial execution and competing in the global cancer marketplace, the time is right for a new leader, particularly one with strong track record of building successful oncology commercial brands.

Richard, of course, is no stranger to Karyopharm, having served on our Board of Directors since February 2020, and prior to his new role here, Richard served as Chief Executive Officer of Ipsen North America and he is the former Vice President and General Manager of Oncology at Amgen. Richard will provide some of his thoughts regarding Karyopharm's future at the end of today's review of our Q1 2021 earnings and business update.

Please now turn to Slide 5. Total revenues were $23.3 million with XPOVIO net product sales of $21.7 million in the quarter. Importantly, XPOVIO prescription demand increased 17% in Q1 2021 as compared to Q4 2020 following the expanded FDA indication granted in December of 2020. We also saw more than 160 new physicians or accounts prescribing XPOVIO for the first time in the quarter. This quarterly growth occurred with many myeloma brands were flat or declining.

Moving to our pipeline progress, we recently announced that in March of 2021, the European Commission granted conditional marketing authorization for NEXPOVIO in combination with dexamethasone for the treatment of patients with multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, two immunomodulatory agents and an anti-CD38 monoclonal antibody, and who have demonstrated disease progression on the last therapy.

Additionally, we also announced that we have now submitted the clinical data from our Phase 3 BOSTON study as part of the Type II Variation Marketing Authorization Application, formally requesting an expansion of our indicated label in Europe. This submission has now been validated and we expect to have a decision on this application from the European Commission in the fourth quarter of 2021.

Turning now to some other program updates from our ongoing hematological and solid tumor clinical studies. We are pleased to see the first set of data from our Phase 3 SEAL study evaluating XPOVIO in patients with dedifferentiated liposarcoma were recently published, and the first patients have now been dosed in a Phase 3 study in diffuse large B-cell lymphoma.

Finally, on the financial front, we ended the quarter with a strong cash position of approximately $233.6 million, that, along with expected future revenues, we anticipate will be sufficient to fund our planned operations into late 2022.

Let's now turn to Slide 6, where I'll provide additional details on XPOVIO's recent sales performance. First quarter net XPOVIO sales increased by 7% as compared to the fourth quarter of 2020, while prescriptions increased by approximately 17%. This increase was primarily driven by multiple myeloma new patient starts. Additionally, we've seen strong payer coverage since the expanded approval received from the FDA in December.

I will note that much of the difference between the sales growth and prescription growth was driven by higher gross-to-net discounts, which are fairly typical in the first quarter of the year as commercial and Medicare patients' out-of-pocket payment requirements reset for the new year. There were also some additional stocking within our distributor network at the end of 2020 in preparation for the launch of XPOVIO's expanded indication.

While we expected higher demand growth, we are encouraged that sales and prescription demand returned to growth in the first quarter and we remain confident in XPOVIO's long-term commercial potential and our ability to further increase utilization.

Richard's top priority in the coming weeks and months ahead of us will be to help our organization further accelerate the growth trajectory for XPOVIO in the U.S. market. We believe some of this will occur naturally as we expect to see the benefit of the longer duration of XPOVIO treatment in the second half of 2021, and we also believe our teams will have better access to customers in the second half of the year, which will increase promotional impact.

Please now turn to Slide 7. Here you can see a chart of monthly XPOVIO prescriptions for the first three months of 2021. Importantly, we saw a significant increase in March and we'll be working hard to further expand utilization and penetration into the earlier line treatment setting in the near future.

Moving now to Slide 8, the graph here shows the prescription refill rate for XPOVIO for both the first and second refills for those patients eligible for these refills. These numbers have remained encouraging throughout 2020 and into 2021, and are significantly higher as compared to our initial launch period in 2019. These refill rates, coupled with average -- an average of nearly three treatment cycles per patient, further reinforced the positive feedback we received from patients and physicians regarding our experience and uses of XPOVIO. Importantly, we do expect the average duration of treatment to increase throughout 2021 as more and more patients are being treated with a once-weekly XPOVIO dose and as part of a combination triplet regimen. Additionally, patient discontinuation rates due to side effects remains relatively low at 12%, which we believe is a testament to more and more physicians getting comfort in helping their patients prevent and manage side effects from XPOVIO with proper prophylactic therapies and dose modifications.

On Slides 9 and 10, you can see our most current robust clinical development plan for XPOVIO in both hematological malignancies and solid tumors. This includes our Phase 3 SIENDO study in patients with endometrial cancer, where we expect to have top-line data before the end of this year and which I'll highlight in more detail in a few moments.

I will note that there are two important clinical trials we expect to initiate in 2021, which we believe will help further define the broad clinical utility of XPOVIO as a potential partner of choice with other active anti-cancer agents. First, we expect to start a new randomized Phase 3 study evaluating XPOVIO in combination with Pomalyst and dexamethasone in patients with previously treated myeloma that will begin in 2021. If the results of this trial are positive, this regimen could represent a potent all-oral drug option to patients with refractory myeloma.

Next, we plan to initiate a new Phase 2 study evaluating XPOVIO in combination with Keytruda in patients with newly diagnosed or recurrent metastatic melanoma. We're particularly excited about this study based on some encouraging data from an investigator-sponsored trial from MD Anderson, evaluating this combination regimen, which was presented at the annual ESMO conference in 2020.

Moving to Slide 11, I'll highlight the potential opportunity of XPOVIO in patients with endometrial cancer where we are currently conducting our Phase 3 SIENDO study. Endometrial cancer is the most common gynecologic cancer in the U.S., with over 65,000 new cases and unfortunately over 12,000 new deaths in 2020. While most women are diagnosed with early stage disease and have a good prognosis after surgery alone, approximately 14,000 patients each year in the United States have advanced or metastatic disease and are treated with combination chemotherapy in the front-line setting.

When their disease progresses, these patients are typically treated with additional chemotherapy, immunotherapy and/or targeted agents. However, currently, there are no approved drugs in the maintenance setting for patients who've had a response to their front-line chemotherapy. This is a setting in which we're currently studying XPOVIO in the SIENDO study. A similar approach was taken with PARP inhibitors for patients with ovarian cancers and their use in this maintenance setting in that disease has been quite dramatic.

To put our potential opportunity in endometrial cancer's perspective, assuming about two-thirds of front-line patients responding to chemotherapy, there could be 3,000 or so patients treated each year in the maintenance setting by capturing approximately 30% of this market.

Now, as we move the Slide 12, you will see highlights from our previous Phase 2 study published in 2019, which evaluated selinexor in 114 patients with heavily pre-treated and actively progressing gynecologic cancers, including 23 patients with heavily pre-treated endometrial cancer who previously received a median of two and up to five prior lines of therapy. In this population with growing cancer, patients treated with single-agent selinexor demonstrated a disease control rate of 35% and a confirmed partial response rate of 9%. The most common side effects were similar to other selinexor studies and included nausea, fatigue, decreased appetite, vomiting, weight loss, anemia, thrombocytopenia, dysgeusia and blurred vision, and where primarily grades 1 and 2 and reversible.

On the right-hand side of the slide, you can see a waterfall plot of the best percent change in the sum of all the target lesions from screening for 19 evaluable patients with endometrial cancer. This encouraging clinical data in a population with highly refractory progressive endometrial cancer gave us the confidence to conduct the SIENDO study in the front-line maintenance setting, which is summarized on Slide 13.

SIENDO is enrolling approximately 248 patients, randomized two to one to receive either 80-milligram selinexor once weekly or matching placebo. Eligible patients included those who have completed a single line of at least 12 weeks of taxane-platinum combination chemotherapy and achieved either a partial or complete response. The primary endpoint of the trial is improvement in progression-free survival from the time of randomization until death or disease progression.

In November 2020, we announced the trial passed its planned interim futility analysis and so the study continues as planned with no modifications, and we expect the top-line data by the end of this year. We remain highly encouraged by this study and the opportunity for patients, should the trial meet its primary endpoint, and we look forward to providing additional updates in the future.

With that, I'll now turn the call over to Mike Mason to review the quarterly financials. Mike?

Michael Mason -- Chief Financial Officer

Thank you, Michael. Since we issued a press release earlier today with the full financial results, I will just focus on the highlights, which begin on Slide 15.

Net product revenue for the first quarter of 2021 was $21.7 million compared to $16.1 million for the first quarter of 2020. The estimated gross-to-net discount for XPOVIO in Q1 2021 was slightly higher at 21% on the top of our expected range of 15% to 20%. License and other revenue for the first quarter of 2021 was $1.5 million compared to $2.1 million for the first quarter of 2020.

R&D expenses for the first quarter of 2021 were $37.1 million compared to $34 million for the first quarter of 2020. The increase in R&D expenses in 2021 compared to 2020 was primarily attributable to costs incurred related to our ongoing clinical trials and regulatory activities.

Selling, general and administrative expense for the first quarter of 2021 was $37.7 million compared to $30.7 million for the first quarter 2020. The increase in SG&A expenses compared to the prior year was due primarily to activities to support the U.S. commercialization of XPOVIO.

On Slide 16, you can see that cash, cash equivalents, restricted cash, and investments as of March 31, 2021 totaled $233.6 million, compared to $276.7 million as of December 31, 2020.

Finally, based on our current operating plans, Karyopharm expects non-GAAP R&D and SG&A expenses, which exclude stock-based compensation expense, for the full-year 2021 to be in the range of $280 million to $300 million. The Company expects that its existing cash, cash equivalents, investments and the revenue it expects to generate from XPOVIO product sales and other license revenues will be sufficient to fund its planned operations into late 2022.

We are not providing revenue guidance for 2021 today as we remain the initial launch phase of XPOVIO and its expanded indication, but do expect to see meaningful growth in 2021 relative to 2020 with the ramp of sales increasing in the second half of the year, as we expect to see the benefit of a longer duration of treatment for multiple myeloma patients being prescribed XPOVIO earlier in their treatment course and/or in combination with Velcade.

I'll now turn the call over to Richard for some of his thoughts about Karyopharm's future. Richard?

Richard Paulson -- President and Chief Executive Officer

Thank you, Mike. Let me begin by saying how excited I am to be leading the Karyopharm organization in such inspiring times. Of course, Karyopharm is not new to me as I have served on its Board of Directors since February of 2020.

And first, I would like to acknowledge and thank Dr. Michael Kauffman for his immense contributions to the scientific and initial commercial success achieved by Karyopharm. Dr. Kauffman, both as a clinician and drug developer, has truly enabled our Company to reach amazing scientific and clinical achievements. During my tenure on the Board, I've been extraordinarily impressed with what this amazing company has been able to do in such a short period of time.

Now, with three separate FDA approvals and one conditional European marketing authorization granted, all having being achieved in just the past few years. Of course, all of these approvals were preceded by many years of careful and thoughtful clinical development for XPOVIO, and Karyopharm remains deeply rooted in innovative science with a passion for improving the lives of patients battling cancer, something that is very near and dear to me as a passion I work toward.

Importantly, I believe the best is yet to come for both Karyopharm and for the patients we aim to serve. However, I know that a lot of work still remains. As Karyopharm is now effectively transitioned to a commercial-stage organization, I am excited to lead the Company in its next chapter as we seek to expand XPOVIO's impact across indications and geographies.

I look forward to leveraging my experience in global product commercialization and organizational leadership to help further advance Karyopharm's impact in helping improve patient outcomes, and I'm excited to work alongside of both Michael and Sharon on behalf of our patients, employees, partners, and shareholders.

Regarding my initial priorities, in the near term, I think we have a great opportunity to expand our breadth and depth in the multiple myeloma treatment landscape where we have really just begun to scratch the surface regarding where we can compete and help patients. And as we continue to generate additional combination data with other myeloma drugs, we believe XPOVIO has the opportunity to become an increasingly important backbone therapy. And moving beyond multi-myeloma, I believe XPOVIO can become a portfolio in a pill with the potential to have clinically meaningful utility across a host of cancers, including many solid tumor indications, both as a single agent and importantly as a future combination partner of choice with other cancer medicines allowing for synergistic opportunities to further help patients battling cancer.

Now, before we open the call up to your questions, let me highlight a few of the key commercial, clinical and regulatory milestones that we have already achieved so far in 2021 and others that we expect for the remainder of the year and shown on Slide 17.

First, we have made significant progress in Europe, where we recently received conditional marketing authorization for an NEXPOVIO and have submitted a Type II variation application based on the Phase 3 BOSTON study, which was recently validated by the EMA.

Next, while we have made some progress increasing XPOVIO sales in U.S., we are far from content here and remain committed to further penetrating the U.S. market throughout the remainder of this year and beyond. This is where I intend to spend much of my time in the weeks and months ahead.

And finally, in the second half of this year, we expect top-line data from the Phase 3 SIENDO study in endometrial cancer, the initiation of multiple clinical trials and the presentation of additional combination data with XPOVIO and other cancer therapies at a variety of medical meetings. I look forward to updating the investment community on our continued progress in the months and quarters ahead.

And with that, I would now like to ask the operator to open the call up to the question-and-answer portion of today's presentation. Operator?

Questions and Answers:

Operator

Thank you. We will now begin the question-and-answer session. [Operator Instructions] Our first question comes from Brian Abrahams from RBC Capital Markets. Please go ahead.

Brian Abrahams -- RBC Capital Markets -- Analyst

Hi there. Thanks for taking my questions. And I guess, first off, congratulations to Michael and Sharon on all your accomplishments. I want to wish you the best of luck in your new roles, and congratulations to Richard as well.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Thanks, Brian.

Richard Paulson -- President and Chief Executive Officer

Thanks Brian.

Brian Abrahams -- RBC Capital Markets -- Analyst

My first -- yeah, so first off, I just -- I'm curious if you could maybe provide a little bit more color around XPOVIO use patterns in the U.S. in the earlier-line population. Maybe can you help characterize the blend of the penta-refractory versus earlier-line BOSTON population being put on drug based on your market research? And how -- what's your sense as to how XPOVIO is fitting into the current competitive landscape across lines versus in previous quarters? And then I had a follow-up. Thanks.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Sure. I'll turn this to John Demaree, our Chief Commercial Officer. John?

John Demaree -- Chief Commercial Officer

Thanks, Michael. The sales growth we saw, Brian, was across lines of therapy with the majority coming from later line patients. It's hard to tell for sure if prescription data we received from our specialty pharmacies and distributors does not capture in what line of therapy patients are receiving XPOVIO.

However, from secondary market research data we purchase our own market research with prescribers and ad boards, our sense is that still much of the business is coming from later lines, e.g., fourth line and later lines, though many of those patients are now receiving the triplet combination with XPOVIO and another myeloma backbone instead of just XPOVIO plus dexamethasone, which is more common in the past, indicating we're getting trial of the new triplet indication and we would expect them to trial in later lines and then move it up into earlier lines if they have success. So while the majority of patients are still in later lines, we are making inroads with some physicians who are starting to prescribe XPOVIO to their second- and third-line patients.

Brian Abrahams -- RBC Capital Markets -- Analyst

Got it. That makes a lot of sense. And then maybe just as a follow-up, just maybe a bigger picture strategic question for Richard. Selinexor, obviously, has shown signals in a number of different tumor types. Where do you see the most promising opportunities for the drug? And do you see any opportunity to further refine the development strategy or even maybe a partner in some of these combo indications you mentioned to split economics to enable any further cost savings on the R&D side? Thanks.

Richard Paulson -- President and Chief Executive Officer

Thanks, Brian. We'll get into that in the future and share with you and the other analysts. But I think in the near term, we have a great opportunity to really expand our breadth and depth in multi-myeloma treatment landscape. And as you know, we've just begun there, and John talked to that, as we're starting to move into earlier lines where we can compete and help more patients.

As you heard from Michael, we are generating new data in the XVd study. As we continue to generate an additional combination data with other myeloma drugs, I do believe we have the opportunity to be a backbone in many areas. And as we move forward and as we heard a little bit around SIENDO moving beyond multi-nyeloma, I really believe this opportunity to be a portfolio in a pill is clinically meaningful for us and will allow us to have a utility across a host of cancers.

So, we have to explore moving forward how we bring that to life. But when we look at many solid tumor indications, both as a single agent and importantly, as you touched on, as a combination partner of choice to other cancer medicines, it's going to allow us to really synergistically bringing XPOVIO to more patients battling cancer moving forward.

Brian Abrahams -- RBC Capital Markets -- Analyst

Got it. Thanks so much.

Operator

The next question comes from Maury Raycroft from Jefferies. Please go ahead.

Maury Raycroft -- Jefferies, LLC -- Analyst

Good morning, everyone, and I would like to add my congrats to Michael, Sharon and Richard, too. Maybe first question is just if you can talk more about the higher gross-to-net discounts in 1Q compared to 4Q '20, can you say what the discount was in 1Q and will this continue going forward or how should we think about it?

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Sure. Yeah, I think -- so we've guided that we'd end up in a range of 15% to 20% for growth and that we ended up just slightly north of that in Q1 at 21%, and pretty typical where the first quarter with the copay resets, etc. So we do expect that to come down into our range of 15% to 20% as we think about for the entire year with some lumpiness quarter to quarter.

Maury Raycroft -- Jefferies, LLC -- Analyst

Got it. That's helpful. And then as far as access for the sales team goes, can you provide any more specifics or quantify how much access they have currently and where you aim to get in the second half of '21?

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Sure. John will take that.

John Demaree -- Chief Commercial Officer

Yeah. So in terms of access to customers, COVID has been a challenge. It created an impact for patients for HCPs in the entire industry and we do still have some access challenges. We do see that growing. It's growing at a different pace in different parts of the country. The last secondary data report that we saw suggested that about 20% to 25% of our interactions are in-person and 75% to 85% of our interactions are still virtual.

We're providing our teams tools to engage with their customers in both the virtual and in-person environments, so they will continue to drive the BOSTON message as we go forward. We expect as we go throughout the remainder of the quarter and amount[Phonetic] the remainder of the year that access in-person to our customers will continue to grow substantially.

Maury Raycroft -- Jefferies, LLC -- Analyst

Got it. Okay, thank you for taking my question.

John Demaree -- Chief Commercial Officer

Thank you.

Operator

The next question comes from Peter Lawson from Barclays. Please go ahead.

Peter Lawson -- Barclays -- Analyst

Hi. Michael, just always been a pleasure speaking with you and best of luck for the next steps. And maybe the first question, just -- Richard just on -- as we get really transfixed on first 100 days, so just wonder if you could walk us through what you're thinking for the initial steps at Karyopharm?

Richard Paulson -- President and Chief Executive Officer

Yeah. Thanks. Thanks, Peter. In initial steps, I think over the next 100 days, I mean really what I'm super excited about with Karyopharm is the opportunity to help patients. As you know, XPOVIO, I think, is uniquely positioned with its broad mechanism of action and its ability to be combined with a variety of other cancer drugs. Now it's going to enable us to make a tremendous impact on patients battling cancer.

In the near term, as we touched on, our focus is to continue to move up past the initial launch of XPOVIO in penta-refractory multiple myeloma. The initial launch was successful, but as we expand into earlier-line settings, it's more complex and it's going to require us to really expand our breadth and depth. So that is a key area of focus for me in the near term.

And then also, should the Phase 3 SIENDO study in endometrial cancer proved successful, we will need to start launch preparations early in the next little while. So -- and this is potentially a significant commercial opportunity for us moving forward. We're going to need to see how we bring that to life over the near term. So those are a couple of areas of my near-term focus.

And finally, as we are in the process of discussing and evaluating potential partners in Europe and Japan with the recent marketing authorization in the EU as well as the acceptance of the MAA for BOSTON indication, which is where we know much of our value to us and potential partners will be generated, we need to continue to explore those partnership opportunities. And the immediate priority is around ensuring we bring NEXPOVIO to the EU in multi-myeloma. However, potential partners have also expressed very high interest in our solid tumor pipeline. So as we touched on, making sure we find the right strategy moving forward in Europe is also going to be a key focus.

Peter Lawson -- Barclays -- Analyst

Got it. Thank you. And then just from your prior experience, Richard, what parallels do you have with drugs similar to selinexor?

Richard Paulson -- President and Chief Executive Officer

Yeah. Thanks, Peter. In the past, I've had the opportunity to bring drugs to market in multi-myeloma, specifically working on Kyprolis. And I think as we know, in many areas when you first launch in later stages of the disease and then work to move up, we need to continue to work with physicians to help them better understand the medicine, help them understand how to initiate and manage patients, and that's a process that takes time, but one which we're committed to moving forward.

Peter Lawson -- Barclays -- Analyst

Perfect. Thanks so much. Congratulations. I will get back into queue.

Richard Paulson -- President and Chief Executive Officer

Thank you.

Operator

The next question comes from Eric Joseph from J.P. Morgan. Please go ahead.

Eric Joseph -- J.P. Morgan -- Analyst

Thanks for taking the questions. Good morning, and congrats again on the role, Richard. I will do my best to not call you Paul Richardson.

Richard Paulson -- President and Chief Executive Officer

Thank you.

Eric Joseph -- J.P. Morgan -- Analyst

Couple of questions...

Richard Paulson -- President and Chief Executive Officer

[Speech Overlap] multi-myeloma.

Eric Joseph -- J.P. Morgan -- Analyst

Right. Just a couple of questions on recent prescription trends and looking forward here, exiting first quarter, growth seems pretty strong. I guess, could you comment on demand trends through April so far? And are you able to perhaps guide us a little bit on second quarter expectations?

And then just a follow-up on sort of where you're seeing use right now, you note that with once weekly -- sorry, with most of the demand being for the once-weekly regimen suggested with the combination use, is there any expectation that that might kind of approved to longer average duration on therapy or is it really more about trying to expand into earlier-line usage that we might see that the benefit of -- longer time what therapy accruing [Phonetic] to sales? Thanks for the taking the question.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Eric, it's Michael. Listen, we're not going to comment on this quarter's growth at all at this point, and we'll update you obviously when we can. But I will turn it over to John for the second part of the question.

John Demaree -- Chief Commercial Officer

Yeah. Looking at our dosing -- thanks for your question there, Eric, just as an example, last year in Q1, over 50% of our new patients were being started on the twice-a-week 80-milligram dose or 160 milligrams per week, which was the starting dose in the STORM population. In this most recent quarter, only 15% of patients were started on that dose, with the remaining 85% being started on a once-weekly dose, most commonly either 100 milligrams or 80 milligrams.

And while we can't be exactly sure which line of treatment these prescriptions are being generated in, syndicated market research we purchased suggests many of them are being prescribed with other multiple myeloma drugs, such as Velcade from the BOSTON study or with Pomalyst or Darzalex which are in NCCN guidelines or with Kyprolis which has been studied in the STOMP trial.

So we continue to see that the triplet use expand, most likely in the later line populations now and we do expect that to move earlier as patients get more comfortable using XPOVIO with the different triplet combinations. Of course, I mentioned a couple of different drugs listed in NCCN, as a company we will only promote the XVd indication which is our on-label indication.

Eric Joseph -- J.P. Morgan -- Analyst

Okay, got it. Thanks for the taking the questions.

Operator

The next question comes from David Lebowitz from Morgan Stanley. Please go ahead.

David Lebowitz -- Morgan Stanley -- Analyst

Thank you very much for taking my question. Is it fair to say that the -- almost all the incremental increase in prescriptions is from the expanded label or is there some incremental increase from the DLBCL and maybe some additional from the initial indication?

John Demaree -- Chief Commercial Officer

I think it's fair to say that the 17% demand growth was driven primarily by new patient starts in multiple myeloma, with most of that being an increase in triplet usage, so driven by the new indication that we've seen.

David Lebowitz -- Morgan Stanley -- Analyst

How do you expect -- I guess, if there's any way to qualitatively, I guess, estimate how the shift in the environment as patients are starting to see their doctors a little bit more actively with vaccinations going up as the year goes on, how could that number shift going forward and how should we look at that when we model as far as what type of demand could change going forward?

John Demaree -- Chief Commercial Officer

I think it was interesting to see in the first quarter, when you look at all the multiple myeloma brands that had reported this quarter to date as Michael mentioned, it seems to be a down quarter in terms of multiple myeloma. We would expect as patients are vaccinated, that patients will return to see their physicians, that they will be getting new therapies. So we would expect the market to return to growth. We would expect to benefit from that market growth as well as obviously incremental growth above that with the continued launch and success in driving uptake in earlier lines with the BOSTON indication.

David Lebowitz -- Morgan Stanley -- Analyst

Thanks for answering my questions.

John Demaree -- Chief Commercial Officer

Thanks for your question.

Operator

The next question comes from Jonathan Chang from SVB Leerink. Please go ahead.

Jonathan Chang -- SVB Leerink -- Analyst

Good morning, and thanks for taking my questions. First question, given it sounds like the majority of revenue currently is still coming from the later line STORM setting or the later line setting period, can you speak to reasons for confidence that you'll be able to successfully penetrate earlier-line settings and see that benefits a longer duration of treatment in the second half with those[Phonetic] numbers?

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Maybe I'll start, and then I'll turn it to John, and Richard may have a comment. The main driver here is education of physicians. Physicians over the last five years have assembled a series of multiple different triplet therapies typically that they use in first, second, third and fourth line settings and they're comfortable with those. We're a new entry.

While this is not the unmet medical need that we had when we went into penta-refractory, we do have one of the simplest, if not the simplest, triplet therapy in terms of administration time required for a patient to come into clinic and so on of all the drugs. So what you're doing now is having to educate doctors that there is a new kit on the block and that it's quite simple, it's easy, and with the proper prophylaxis, it can be very manageable with patients on this combination, as you know, for over two years now. So that's the main driver here.

And I think as John mentioned with our sales force getting back face to face, we will be able to change practice and guide physicians that there is a new option out there. John, do you want to?

John Demaree -- Chief Commercial Officer

Yeah. I think Michael's point about education is critical, and we're also deploying a number of new tools to help continue to reinforce and drive that education. So we're deploying interactive content that can be used in-person or via virtual engagements by both our sales force and our marketing team.

In addition, we recently made significant investments in our digital ecosystem to improve that physician education, including website enhancements, KOL videos, banner ads, search engine marketing, search engine optimization, digital media, social networking, competitive media pilots, and plan to continue to expand this substantially going forward to drive that education that Michael spoke to as being critical.

We're also investing in significant peer-to-peer education via both live and digital channels. And finally, beyond just branded, we're continuing to enhance disease state education around the role of XPO1 inhibition in cancer, including in multiple myeloma. So a number of things that we're doing to continue to drive that education in the second half of the year -- second quarter and second half of the year.

Jonathan Chang -- SVB Leerink -- Analyst

Got it. Thank you. And just one follow-up to that. Can you give us a sense of what you can and can't track in teasing out where these sales are coming from? Thank you.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

John?

John Demaree -- Chief Commercial Officer

Yeah. So...

Ian Karp -- Senior Vice President, Investor and Public Relations

Do you want me to -- so I'll just -- this is Ian. Yeah, Jonathan, yeah, not much has really changed there for those who have been following our story for some time. Essentially, we're able to track from our distributor network. Certainly, for about half of our business that goes through special distributors, we can see essentially just what dose of drug is being prescribed and how much per account.

And then for the other half of our business, we're able to see a bit more data where we can see are these new patients, are they refills and that's where we get our refill data from, and we can see if are these multiple myeloma patients or are these DLBCL patients. But none of this data unfortunately gives us specifically what line of treatment these patients are from, and it doesn't tell us what specifically combination drugs are being prescribed as [Technical Issues]. So all of that information we garner through general market research or intelligence with our sales force, etc.

Operator

The next question comes from Ed White from H.C. Wainwright. Please go ahead.

Ed White -- H.C. Wainwright & Co. -- Analyst

Good morning and congratulations to Richard, and a thank you and congratulations to Michael and Sharon as well. So, just two pipeline questions. The first is on XPORT 035 and 034 in myelofibrosis, I was just wondering if we can get a status update and perhaps when we can see data from those studies?

And the second question is on the solid tumor studies and just wanted to get an update there on GBM non-small cell lung cancer and colorectal cancer, any kind of updates you can give us there on status and timing to data would be appreciated as well? Thank you.

Richard Paulson -- President and Chief Executive Officer

Hi, Ed. We will update on the -- I know the 034 and 035 myelofibrosis studies are on clinicaltrials.gov. When we have our first patients enrolled, we will announce those as typical. We won't be able to give much in the way of data expectations, just given accrual rates and so on and so forth. But we're quite encouraged about the underlying basis for doing those studies, and hopefully, this year, you guys will see some data in that regard.

For the solid tumor studies, the same thing applies. The colorectal and lung studies are ongoing, and we hope to provide updates in medical meetings when appropriate, hopefully this year. And for the GBM study, similar, although I think we've just initiated, as you know, some of the new cohorts in front-line combination and in relapsed in combination with lomustine, so those will take a little bit longer and I would expect maybe next year to see them, but we'll have to see.

Ed White -- H.C. Wainwright & Co. -- Analyst

Great.

Operator

The next question comes from Colleen Kusy from Baird. Please go ahead.

Colleen Kusy -- Baird -- Analyst

Hi, good morning. Thanks so much for taking our questions, and congrats to the whole team. If you could comment on what the inventory stocking level is as of the end of 1Q? And then when you're thinking about competition in the later lines in multiple myeloma, as what are some of the features that XPOVIO or the features of XPOVIO that really resonates with the prescribers when thinking relative to competitors?

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Mike Mason will discuss the inventory.

Michael Mason -- Chief Financial Officer

Sure. So, as Michael mentioned earlier in the call, we had 17% demand growth with 7% ex-factor growth, and part of that was gross to net and part of the other difference was some stocking that happened in December of 2020. If you recall, we got the BOSTON approval in mid-to-late December, so we saw some stocking in December. So that -- we start -- we didn't see much of a benefit of that in Q1, so that let us somewhere around four-ish weeks of inventory, which is pretty consistent with what we've had in prior quarters.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Great. John will take the second part.

John Demaree -- Chief Commercial Officer

Yeah. In terms of what customers are looking for, you ask in later lines of therapy, actually, our goal with the BOSTON data is to move into earlier lines of therapy. And what we've seen there in multiple myeloma, physicians -- many physicians believe it's important to treat with different mechanisms as early as possible in the patients' course of disease. And that's one of the key advantages XPOVIO brings as a novel mechanism of action that is synergistic with proteasome inhibitors like Velcade in the indicated XVd regimen.

We also know that they are very focused on efficacy and we're able to communicate with the XVd regimen rapid and sustained PFS benefit, as well as clinically significant durable responses, all attributes that are very important to the customers.

And I do think it's important to note, when you look at the landmark BOSTON study, it's the only trial out there to date that study Velcade weekly, the way it's actually used by clinicians in clinical practice. And despite using that weekly dose or half a dose of other trials, it still produced very strong data for patients. So those are some of the attributes that our physicians are looking for and we're highlighting as we work to move XVd up into earlier lines of therapy.

Colleen Kusy -- Baird -- Analyst

Great, thank you. It's really helpful. And if I can quickly ask a follow-up, is SIENDO data are positive? How much incremental investment would you expect you'll need to make in your commercial infrastructure to expand into solid tumors?

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Yeah. Go ahead, John.

John Demaree -- Chief Commercial Officer

So we're actually doing that assessment right now to look at overlap of accounts and the size of the commercial platform and footprint that we would need to fully maximize that. So that's something that we'll be able to provide more data to you at a later point in time.

Colleen Kusy -- Baird -- Analyst

Great. Thank you.

Operator

The next question comes from Arlinda Lee from Canaccord. Please go ahead.

Arlinda Lee -- Canaccord -- Analyst

Hi, guys, thanks for taking my questions. I guess I was curious about on the education front. I'm curious what you guys are encountering is what if the disconnect is or the hurdle is for prescribers to prescribe more into the BOSTON trial or BOSTON patient population? Thank you.

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Yeah, I'll start and John can add. I don't think there's really a disconnect. Again, I think it really has to do with -- that you do things that you are used to doing, doctors are very much confident with what regimens they had prior to the BOSTON approval. They've been working on them and owning them for the last five years, which is really the last time that a major second-line new indication, our new drug came out. And so they're just comfortable. It's a little like -- before we all use seatbelts, nobody really wanted to put it on, but you eventually get used to it and then it becomes second nature.

So what we have to do is make the BOSTON regimen second nature to physicians, and that's going to take a little bit of time, but I don't think there is a problem here at all. When the doctors -- typically most doctors when they use this regimen, they're pleasantly surprised. When they use proper prophylaxis, we get a number of doctors calling us and saying, well, the patient didn't have any nausea. And we asked them what they did, and they said, well, I used what you suggested and that's how it all works. So we know how to prevent the side effects from this drug, a lot of them, and they are reversible and we just have to change people's habits.

John Demaree -- Chief Commercial Officer

And Michael is absolutely right. Some physicians have a habit based on the STORM data. As you know, the once-weekly dosing regimen in the BOSTON is better tolerated into the higher level of efficacy. So it's just getting physicians to try that new regimen versus the original regimen we launched, but continue that education process.

Operator

And there are no more questions in the queue. This concludes our question-and-answer session. I'd like to turn the conference back over to Richard Paulson for any closing remarks.

Richard Paulson -- President and Chief Executive Officer

I would like to thank everybody again for joining today's call and we look forward to updating you on our progress as soon as we can. Thank you, operator, you can close the call.

Operator

[Operator Closing Remarks]

Duration: 46 minutes

Call participants:

Ian Karp -- Senior Vice President, Investor and Public Relations

Michael G. Kauffman -- Co-Founder, Senior Clinical Advisor

Michael Mason -- Chief Financial Officer

Richard Paulson -- President and Chief Executive Officer

John Demaree -- Chief Commercial Officer

Brian Abrahams -- RBC Capital Markets -- Analyst

Maury Raycroft -- Jefferies, LLC -- Analyst

Peter Lawson -- Barclays -- Analyst

Eric Joseph -- J.P. Morgan -- Analyst

David Lebowitz -- Morgan Stanley -- Analyst

Jonathan Chang -- SVB Leerink -- Analyst

Ed White -- H.C. Wainwright & Co. -- Analyst

Colleen Kusy -- Baird -- Analyst

Arlinda Lee -- Canaccord -- Analyst

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