Mersana Therapeutics, Inc.

Good morning and welcome to Mursana Therapeutics' second quarter 2021 conference call and webcast. Currently, all participants are in a listen-only mode. There will be a question and answer session at the end of this call. I'd now like to turn the call over to Sarah Carmody, Executive Director, Investor Relations Incorporate Communications. Please proceed.

Good morning. Welcome to Mursana's second quarter 2021 conference call. Earlier today, we issued a press release reviewing our second quarter financial results and business updates, which will be covered on this call. A replay of today's call will also be available on the investor and media section of our website. After our prepared remarks, we will open the call for Q&A. Before we begin, I'd like to mention that our call will contain forward-looking statements within the meaning of federal securities law. These are not statements of historical facts and are based on management's beliefs and assumptions and on information currently available. They are subject to risks and uncertainties that could cause the actual results and the implementation of the company's plans to vary materially, including the risk that results of our ongoing or future clinical studies may be inconclusive with respect to the efficacy of our product candidates, that we may not meet clinical endpoints with statistical significance, or there may be safety concerns or adverse events associated with our product candidates. that preclinical testing or early clinical results may not be predictive of the results or success of our ongoing or later preclinical or clinical studies, that the identification, development, and testing of the company's product candidates and new platforms will take longer and or cost more than planned, and that our clinical studies may not be initiated or completed on schedule, if at all. These risks are discussed in the company's SEC filings, including, without limitation, the company's quarterly report on 10-Q, filed on May 10, 2021, and subsequent filings. In addition, while we expect that the COVID-19 pandemic might adversely affect the company's preclinical and clinical development efforts, business operations, and financial results, the extent of the impact on the company's operations and the value of and market for the company's stock will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, the severity of additional strains of the virus, travel restrictions, quarantines, physical distancing, and business closure requirements in the US and in other countries, and the effectiveness of actions taken globally to contain and treat the disease. Except as required by law, the company assumes no obligation to update these forward-looking statements publicly even if new information becomes available in the future. And with that, I'll turn the call over to Anna Protopopis, MRSANA's President and Chief Executive Officer. Thank you, Sarah.

Good morning and welcome to our second quarter 2021 Corporate and Financial Update Call. Joining me today with prepared remarks is Brian Descheidner. I am also joined by the rest of the executive team who will be available for your questions. At Mursana, our key focus for the first half of this year has been executing on our goals. Our goals associated with building UPRI as a foundational medicine in ovarian cancer and building out our innovative pipeline of ADCs addressing areas of high unmet medical need. I am very pleased to report that we have made significant progress on both UPRI and the pipeline. Let me begin with the agenda for today's call. I will start with UPGRADE, our upper recombination trial in platinum sensitive ovarian cancer that has just initiated. Then I will brief you on UPLIFT, a single arm registration strategy in platinum resistant disease. I will also be providing updates on the upper ovarian cancer expansion cohort, the upper lung cancer expansion cohort, as well as XMT-1592, 1660, and 2056. Let me start with UPGRADE. Just last week, we announced that we reached another significant milestone in the development of UPRI with the initiation of patient dosing in UPGRADE, a phase one umbrella study designed to evaluate UPRI in combination with other ovarian cancer therapies. This study will further explore the role of UPRI in platinum-sensitive disease. We're starting the study in combination with platinum, as platinum therapy is currently the mainstay therapy in earlier line platinum-sensitive ovarian cancer, a large opportunity. Moving UPRI earlier, sorry, moving part, UPRI into earlier line of therapy could significantly expand the number of patients with ovarian cancer that could benefit from UPRI and the duration of time over which we can impact their disease. In the current standard of care, platinum and taxane are administered for a fixed number of cycles due to the cumulative toxicities, including alopecia, peripheral neuropathy, and neutropenia. In fact, many ovarian cancer patients have continuing peripheral neuropathy as a result of repeated cycles of the platinum and taxane regimen. This phase one open-label dose escalation portion of the study will determine the maximum tolerated dose and safety and tolerability of a Q4 weekly administration of APRI in combination with carboplatin for six cycles and then continuation with APRI monotherapy in platinum-sensitive patients with high-grade serous ovarian cancer who have received one or two prior platinum-based regimens. This design allows us to assess the advantages of combining with carboplatin and replacing patetaxel, an agent that carries significant toxicities. As a reminder, APRI's current tolerability profile has not included severe peripheral neuropathy or neutropenia which is promising for combination with platinum. We believe this is a key differentiator from other ADC platforms and an important prerequisite for moving into earlier lines of therapy. Importantly, the design of upgrade will also allow us to evaluate the additional benefit of continuing treatment with UPRI as a single agent beyond the six cycles of combination therapy, potentially providing access to a larger population of patients receiving longer durations of therapy. As a reminder, the dose escalation portion of the combination study has the potential to move more rapidly because we know the active doses of platinum and we know the active doses of apri as monotherapy. While it is premature to provide guidance on enrollment timelines at this stage, we do believe that the design of this study could generate a significant amount of data during 2022. We are excited to have this important study underway and look forward to updating you on our progress. Now let me turn to Uplift, a single arm registration strategy in platinum-resistant ovarian cancer. We are encouraged with the interest in the study to date and the engagement of both the US and the EU cooperative groups. As a reminder, we began dosing patients in April with relatively rapid conversion of sites already involved in the expansion cohort. New sites in the US, EU, and other geographies are coming online to further support enrollment projections. The design of Uplift focuses both on increasing the potential for label differentiation and the probability of success. We believe UPLIFT is enrolling a broader patient population than other studies in this space, with more prior lines, more flexible inclusion of prior pervasism of treatment, consistent with the pervasism of label, and with more underlying comorbidities, like baseline peripheral neurography. UPLIFT also offers two shots of gold with a primary endpoint in the nabby to behind population, and a secondary endpoint in the overall population, allowing us to fully evaluate the role of the biomarker in enriching for patient outcomes. In addition, we believe we have carefully designed and executed on the work necessary to be able to embark on uplift with the right diagnostic in place. You will recall from our webinar in April that we have taken a systematic approach to the development of a robust, predictive, and reproducible biomarker. The tumor proportion score of equal or greater to 75 biomarker enriches for responders and has attractive features relative to other kind of approaches to ensure reproducibility anywhere in the world across different labs and pathologies when deployed as a commercial diagnostic. Overall, we're encouraged by the current pace of enrollment in uplift, but we'll refrain from providing further guidance on timing of completion of enrollment. Uplift and upgrade are critical steps in evaluating the potential of UPRI to benefit both patients with recurrent platinum-sensitive ovarian cancer as well as platinum-resistant ovarian cancer. Remember that annually in the U.S., there are approximately 22,000 women newly diagnosed with ovarian cancer. That's not to mention those with fallopian tube or primary peritoneal cancer treated using the same algorithm. Unfortunately, even after frontline therapy, 80% of these patients with relapse, most with platinum-sensitive disease. Ultimately, 14,000 women die of the disease each year. Uplift, our fast-to-market registration strategy, focuses on those 14,000 women in the terminal phase of the disease. With upgrade, we have the potential to address the needs of a larger number of patients earlier in the disease, where we believe we have the potential to deliver longer benefit with increased treatment duration as combination followed by continuation. We believe these studies provide the roadmap for establishing a brief as a foundational therapy in ovarian cancer. Finally, for upper ovarian, let me update you on the status of the expansion cohort. We recently closed enrollment in the ovarian cancer expansion portion of the Phase I clinical study. Given the continued support of investigators, enrollment momentum continued, and we have close to 100 patients enrolled in the expansion cohort. Mining this substantial data set will give us a robust understanding of the profile of UPRI and help us continue to optimize our development strategy. Our goal is to provide an update on the ovarian expansion cohort this year at the appropriate time. Lastly, on UPRI, we are approaching completion of enrollment in the UPRI lung adenocarcinoma expansion cohort. We plan to wait for the entire expansion cohort to be enrolled, evaluable, and mature, and expect to disclose the top-line data and determine our next steps in lung in the fourth quarter. We want to ensure we understand the NAPI-2B status of these patients in order to determine the patient selection strategy, acknowledging that the bar for investment in development of OPRI as a single agent is is high due to the intensely competitive landscape in lung. As we have indicated before, the prevalence of NAPI to be high, as we defined in ovarian cancer cohort, that's the tumor proportion score greater than 75, is substantially lower than in ovarian cancer. It appears only about a third of patients with lung cancer have a TPS equal or greater than 75. This compares to a prevalence of approximately two-thirds for ovarian cancer. In lung, an even higher TPS cutoff might be necessary to achieve the desired response rate, which could further focus the eligible population. Our decision as to the next step will be based on two considerations. Overall efficacy observed in a biomarker-selected population and two, the bar necessary for commercial success given the current and emerging treatments. Turning now to the pipeline, I will start with XMT1592, our dollar synth and ADC targeting NAPI2B. Remember that our strategy is to develop XMT1592 as a second shot on goal based on the differentiated profile seen in preclinical studies in lung models. As we communicated previously, we have exceeded the MTD and continue the ongoing exploration of different doses and regimens and our work to fully characterize the profile of the agent. We expect to complete our evaluation of XMD1592 and disclose top-line data around year-end. Finally, with respect to the pipeline, we have continued to advance our two first-in-class preclinical ADCs addressing areas of high unmet need through IND-enabling studies. For 1660, our B7H4 doulas synth and ADC, in parallel to the IND-enabling studies, we have initiated early diagnostic development work, much like we did with APRI for NAPI2B. We believe this is an important step to ensure that the diagnostic is developed in tandem with the development of XMT1660. For XMT2056, our first immune of Synth and Sting agonist ADC, I'm very excited to announce that Tim Loinger, our Chief Science and Technology Officer, has been invited to present on this program at the upcoming virtual 2021 triple meeting in October as part of a plenary session on drug conjugates. During his presentation, Tim plans to provide further promising preclinical data for XMT 2056 and disclose the target. We look forward to sharing this information and expect to provide more details around the clinical development plan for 2056 later this year. With that, I'll turn the call over to Brian for an overview of our financial results.