John Scarlett
Analyst · Needham
Thanks, Olivia. I'll finish today's discussion with highlights from the data presentations in June at the EHA Annual Congress. As you know, we also hosted the KOL event on June 25 with two of the investigators who reprised the EHA presentations and participated in the question-and-answer session with sell-side analysts. We were encouraged by the interactive dialogue at the KOL event that discussed the significant unmet medical need in both lower-risk MDS that's relapsed and refractory to ESAs as well as in relapsed/refractory MF, and the important role imetelstat can potentially serve in meeting those needs. For lower-risk MDS, Dr. Platzbecker emphasized the meaningful and durable transfusion independence, broad activity and disease modifying potential of imetelstat treatment. For relapsed/refractory MF, Dr. [indiscernible] described how real-world data corroborated the potential OS benefit with the imetelstat treatment that's been observed in IMbark. So now I'd like to review the highlights. First, let's review the updated efficacy and safety data from the 38 target population patients in the Phase II portion of IMerge. The data cutoff date for the presentation at EHA was April 30, 2019, at which time the median follow-up was 15.7 months. As a reminder, IMerge is a two part Phase II/III clinical trial. The primary efficacy endpoint is an eight week TI rate, or simply stated, the proportion of patients who achieved transfusion independence or TI for a period of eight consecutive weeks. Key secondary endpoints include the rate of TI lasting at least 24 weeks or 24-week rate TI and duration of TI. The EHA presentation of the updated IMerge data reported meaningful and durable transfusion independence achievable with imetelstat treatment in heavily transfusion-dependent, lower-risk MDS patients. The importance of all of these was emphasized by both investigators who participated in the KOL event. In particular, the clinically meaningful responses for both eight week and 24-week TI rates and high transfusion-burden patients highlighted imetelstat's potential role as a much-needed alternative treatment in lower-risk MDS. At the American Society of Hematology, or ASH, annual meeting in December 2018, the reported eight week TI rate was 38%. With the addition of two new responders, the reported rate at EHA increased to 42%. The durability of the transfusion independence also improved with the 24-week TI rate of 26% reported at ASH and then increasing to a rate of 29% as reported at EHA. With longer follow-up for patients in this data set compared to ASH, the median duration of transfusion independence for responders was 86 weeks or over 20 months with the longest duration of response reported to be more than 2.5 years. In addition, a total of 26 of 38 patients in the target patient population experienced at least a four unit reduction in transfusion burden. And there was a mean relative reduction of red blood cells transfusion burden of 68% when compared to baseline. These reductions in transfusion burden should lead to an improved quality of life, less time in the infusion chair, less cost and reduced exposure to potential iron overload. Next, as was also emphasized at the KOL event, the updated data from EHA indicated that transfusion independence achievable with imetelstat was broadly distributed among different patient subgroups. This included similar results in patients with baseline transfusion burdens that were either greater than or less than six units. In addition, similar results were observed in both ring sideroblast patient subgroups, that is, RS positive and RS-negative patients. Likewise, patients with baseline serum or erythropoietin levels, both above and below 500 million units per ml, achieved similar transfusion independence with imetelstat treatments. We're encouraged that imetelstat demonstrates activity across these different subgroups, and therefore, that it can potentially be used broadly for the treatment of lower-risk MDS patients. Finally, the updated data from the Phase II portion of IMerge presented at EHA also provided further evidence of potential disease-modifying activity with the imetelstat treatment. This was evidenced by improvement after imetelstat treatment in the cytogenetics of cells and the bone marrow and by reduction in the proportion of cells carrying the SF3B1 mutation, both of which are hallmarks of malignant MDS cells. In addition, the EHA presentation reported 75% of the eight week TI responders also experienced a rise in hemoglobin of more than 3 grams per deciliter, suggesting potential recovery of neural pneumatic [indiscernible]. With these data, we now have three hematologic myeloid malignancies with the evidence of potential disease modification associated with imetelstat treatment. The first was in essential thrombocythemia, the second was in myelofibrosis, and now in the third, in lower-risk MDS. On the safety side, there were no new safety signals. The most frequently reported adverse events were Grade 3 or 4 cytopenias. More than 90% of the neutropenias and thrombocytopenias were reversible within four weeks. To put IMerge Phase II results in the further context, I'd like to say a few words about the data presented at ASH in December from the MEDALIST trial with luspatercept, which was a Phase III clinical trial and compared those data to the data that I just described for imetelstat-treated patients in the Phase II portion of IMerge. We acknowledge the limitation of comparing results from an open-label Phase II trial to a blinded placebo-controlled Phase III trial, and also that luspatercept has a relatively benign safety profile. However, the IMerge Phase II data does suggest that imetelstat efficacy is differentiated from that of luspatercept. For lower-risk patients -- sorry, the lower-risk MDS patients studied in MEDALIST had many similarities to the patients studied in IMerge. They have failed ESAs and had become transfusion-dependent, they were non-del(5q), and they were naive to both lenalidomide and HMAs. However, there was an important distinction. The patient population enrolled in IMerge had a higher disease burden, specifically the median baseline number of pretreatment transfusions for MEDALIST patients was 5 units of packed red blood cells per eight weeks compared to 8 units per eight weeks for the IMerge patients. Notably, 29% of the MEDALIST patients had a baseline transfusion burden of less than 4 units per eight weeks. Those patients would not have been eligible for the IMerge trial, where we required a transfusion burden of greater than or equal to 4 units per eight weeks. Another distinction between the two patient populations is that enrollment for IMerge was open to both RS positive and RS-negative patients, while MEDALIST was limited to RS-positive patients only. When we look at the efficacy results for the two drugs in the two studies, the overall eight week TI rates were similar, 42% for imetelstat-treated patients and 38% from luspatercept. However, upon further analysis of the data from the ASH presentation, in the luspatercept patients with the transfusion burden of greater than or equal to 4 units per eight weeks, that is the population with the baseline transfusion burden consistent with that of the imetelstat patients in IMerge. The eight week TI rate was only 20% for luspatercept. In conclusion, if our upcoming Phase III portion of IMerge is able to demonstrate eight week and 24-week transfusion independence rates within a similar range as was seen in the Phase II portion of IMerge, we expect imetelstat will compare favorably with other drugs, including luspatercept within a broad population of lower-risk MDS patients who were relapse or refractory ESAs. I'd like to next turn to the data presented at EHA and at our KOL event from IMbark. Our Phase II trial of imetelstat in relapsed/refractory intermediate to or high-risk myelofibrosis. In order to further assess the potential overall survival benefit observed in relapsed/refractory MF patients treated with 9.4 milligrams per kilogram of imetelstat every four weeks in the IMbark trial, a series of analyses was conducted in collaboration with the Moffitt Cancer Center, a leading academic cancer hospital in Florida. In the analyses, the median OS from IMbark was compared to the OS calculated from real-world data, also abbreviated RWD, in patients who had discontinued treatment from ruxolitinib and who were subsequently treated with best available therapy such as steroids or chemotherapeutic agents. To make a better comparison between the IMbark data and real-world data, a patient cohort from the Moffitt data set was identified that closely match the IMbark patients using guidelines for inclusion and exclusion criteria as defined in the IMbark clinical protocol, so that's just platelet counting spleen size. A statistical technique known as propensity score analysis was then used to balance key baseline patient characteristics for the two analysis cohorts. Using these statistical approaches, the median overall survival for imetelstat-treated relapsed/refractory MF patients in IMbark was more than double that for the closely matched real-world patients treated with best available therapy. The calculated median OS for the imetelstat-treated patients was 30.7 months, which was more than twice the calculated median OS of 12.0 months using real-world data patients treated with best available therapy. The analyses also indicated 65% to 67% lower risk of death for the imetelstat-treated patients compared to the real-world patients treated with best available therapy. So these analyses corroborated the potential OS benefit observed in the 9.4 milligram per kilogram arm of the IMbark Phase II clinical trial. Although, there are limitations of comparative analyses between real-world data and clinical trial data, these analyses give us confidence that further evaluation of the potential overall survival benefit in relapsed/refractory MF may be warranted. As such, we've been evaluating potential late-stage development approaches and regulatory strategies as we prepare for an end of Phase II meeting with the FDA. We are planning to conduct that meeting by the end of the first quarter of 2020. In summary, we've made great progress since regaining the rights to imetelstat less than a year ago. We've completed the IND transfer. We've assumed full responsibly for the drug. We've built world-class drug development leadership team to achieve future milestones. We reported compelling data at EHA that supports the future development of the imetelstat program in MDS and expect to open the Phase III portion of IMerge later this month. We're also strategically preparing for an end of Phase II meeting with FDA to discuss potential late-stage development scenarios and possible regulatory paths for imetelstat in relapsed/refractory MF. 2019 is proving to be a critical year for Geron, and we look forward to achieving these milestones as we progress through the second half of the year. And with that, we're now happy to answer your questions. I'll turn the call back to our operator.