Lisa Rojkjaer
Analyst · Citi
Thanks, Dave. I will now provide an update on our progress over the last quarter and plans for the year ahead. I'm on Slide 15. Our current hematology and oncology focus areas are the clinical development of R289, our potent and selective dual IRAK1 and IRAK4 inhibitor and our strategic collaborations with academic partners to evaluate olutasidenib in clinical settings beyond relapsed/refractory IDH1 mutated AML. Our Phase Ib study of R289 in patients with relapsed or refractory lower-risk myelodysplastic syndrome, or MDS, is progressing well and updated data from the dose escalation part of the study was recently presented in an oral session at ASH. I'll provide an update on that study as well as our planned next steps for R289 shortly. For olutasidenib, we have a number of strategic collaborations to study olutasidenib in additional therapeutic areas. Through our collaboration with MD Anderson, olutasidenib is being evaluated in 5 clinical studies as monotherapy or combination therapy in patients with a variety of IDH1 mutation-positive hematologic malignancies, including AML, higher and lower-risk MDS, chronic myelomonocytic leukemia, or CMML, and its post-transplant maintenance therapy. In addition, a study of olutasidenib in combination with co-targeted therapy in patients with relapsed or refractory AML with additional signaling pathway mutations is underway. Our second collaboration with the CONNECT Cancer Consortium and the Phase II TarGeT-D study is evaluating olutasidenib in combination with temozolomide followed by olutasidenib monotherapy as maintenance treatment in newly diagnosed pediatric and young adult patients with IDH1 mutation-positive high-grade glioma. First patient was enrolled in the study in October. Lastly, we're also partnering with the National Institutes of Health and National Cancer Institute's MyeloMATCH Precision Medicine Trial Initiative. The planned study will evaluate olutasidenib in first-line IDH1 mutated AML and MDS. We're excited about olutasidenib's potential to provide a new treatment option in these underserved patient populations and look forward to seeing the data that these studies generate in the future. Now I'll discuss R289, our novel dual IRAK1 and IRAK4 inhibitor. Let's start with the treatment landscape for lower-risk MDS. I'm now on Slide 17. MDS is a clonal disorder of hematopoietic stem cells, leading to dysplasia and ineffective hematopoiesis. The main consequences for patients are anemia and transfusion dependence, which adversely impact their quality of life. In addition, infections, iron overload from transfusions and subsequent organ dysfunction all negatively impact the patient. Therapies used in the upfront setting include erythropoiesis-stimulating agents, or ESAs, if patients are eligible or luspatercept. Luspatercept and more recently, imetelstat are also approved for ESA failure transfusion-dependent patients. Finally, while hypomethylating agents or HMAs are also approved, the percentage of patients achieving transfusion independence is low. With 8-week transfusion independence rates approaching 40% with luspatercept and imetelstat, there is still a need for safe, effective therapies for transfusion-dependent lower-risk MDS patients that are relapsed/refractory to or ineligible for ESAs. On Slide 18, you'll see the value proposition of R289 in lower-risk MDS. There are about 12,000 previously treated lower-risk MDS patients in the U.S. And as mentioned on the previous slide, there's a high unmet need for therapies in this disease area, particularly for transfusion-dependent patients. Dysregulation of inflammatory signaling is key to the pathogenesis of lower-risk MDS and IRAK1 and 4 mediate this process. Blocking both IRAK1 and 4 may suppress marrow inflammation and leukemic stem progenitor cell function and restore normal hematopoiesis. R835, the active moiety of R289, blocks toll-like receptor and IL-1 receptor signaling in vitro and was active in various preclinical models of inflammation. Clinical proof of concept of this anti-inflammatory effect came from a healthy volunteer study in which R835 markedly suppressed LPS-induced cytokine release compared to placebo. As a reminder, R289, which is currently being evaluated in the clinic, is the oral prodrug that is rapidly converted to R835 in the gut. R289 has Fast Track designation for the treatment of patients with previously treated transfusion-dependent lower-risk MDS and orphan drug designation for MDS from the FDA, giving the molecule an expedited regulatory pathway, potential priority review and 7 years of market exclusivity upon approval. Both of these designations underscore the agency's interest in this rare disease, the unmet need of the patient population and the FDA's willingness to collaborate with Rigel in the development of R289. R289 has thus far demonstrated a promising clinical profile in our Phase Ib study with encouraging safety and preliminary efficacy data that were highlighted recently at ASH in December. On Slide 19, I'd like to quickly review the design of our multicenter open-label Phase Ib study in patients with relapsed/refractory lower-risk MDS, which aims to evaluate the safety, tolerability, PK and preliminary efficacy of R289 in this patient population as well as select a dose for future studies. The dose escalation phase evaluated 6 different R289 dosing regimens administered once or twice daily using a modified 3+3 design. In the dose expansion part of the study, up to 40 transfusion-dependent relapsed/refractory lower-risk MDS patients will be randomized to receive R289 doses of either 500 milligrams once or twice daily in order to select the recommended Phase II dose for future clinical studies. The first dose expansion patient was dosed in October. We anticipate that we will have sufficient data to make a decision on the recommended Phase II dose in the second half of this year. Once we've selected the dose, we will evaluate R289 in a cohort of less heavily pretreated patients who are relapsed/refractory to or ineligible for ESAs. Now I'd like to walk you through updated safety and efficacy results from the Phase Ib study with the data cutoff date of October 28 that were presented at ASH. On Slide 21, you will see the characteristics of the 33 patients enrolled in the dose escalation part of the study. The median age was 75 and the patients were heavily pretreated with a median of 3 prior therapies with around 70% having received prior luspatercept and HMAs. In addition, the majority of the patients had a high baseline transfusion burden. These characteristics are really representative of the lower-risk MDS population with the highest unmet medical need. Moving to Slide 22, we'll review the safety findings. Overall, R289 was generally well tolerated with a low incidence of Grade 3 or 4 cytopenias and infections. There was one dose-limiting toxicity reported, a Grade 3/4 AST/ALT increase at the 750-milligram daily dose level and no evidence of dose-dependent toxicity across the other dose groups. On Slide 23, the swimmer plot shows an overview of transfusion events by dose group, starting with the lowest dose group, 250 milligrams daily at the top. Red cell transfusions occurring over at 16 weeks prior to start of R289 are shown to the left of the colored bars, establishing the baseline transfusion frequency for each patient. All patients were transfusion dependent, except for 2. The median time on therapy was 5.5 months, ranging from 0.9 months to nearly 28 months of treatment. To be evaluable for hematologic response assessment, patients must have been treated for at least 16 weeks. No response has occurred at 250 milligrams once or twice daily. Of 18 evaluable patients receiving dose levels of 500 milligrams daily or higher, 6 patients or 33% achieved red cell transfusion independence or RBC-TI, lasting for 8 weeks or longer. In 4 patients, RBC-TI lasted for more than 16 weeks and for 3 patients for more than 6 months. The median duration of RBC-TI was around 23 weeks, ranging from 9 weeks up to more than 24 months. Also, the median time to onset of RBC-TI was about 2 months, which is also encouraging. While this is a small data set, we're encouraged by these results given the highly refractory nature of these patients. Slide 24 presents a summary of the patients achieving RBC-TI. All patients had received 2 or more prior therapies, some had received experimental therapies and 5 of the 6 had received prior HMAs. For these patients, peak hemoglobin increases ranging from 2.9 to 6.1 grams per deciliter were also observed, indicating the potential of R289 to improve anemia. In summary, R289 was generally well tolerated with an encouraging safety profile and promising preliminary efficacy in an elderly, heavily pretreated lower-risk MDS patient population. On Slide 25, I will review the next steps for R289. We aim to complete enrollment of the dose expansion phase of the study and selection of the recommended Phase II dose for future studies in the second half of this year. We anticipate sharing top line data from the dose expansion phase by the end of the year. Once the recommended Phase II dose has been selected, we will evaluate R289 in a cohort of less heavily pretreated patients who are relapsed/refractory to or ineligible for ESAs in the same study. In addition, upon completion of the Phase Ib study, we plan to follow up with the FDA to discuss a potential registration study. With its mechanism of action, we believe that R289 has potential in other indications where the pro-inflammatory cascade plays a role, and we'll provide more details as our plans progress. Now turning to our partnered program with Eli Lilly. On Slide 27, I'd like to provide a short update on ocadusertib, the non-CNS penetrant RIPK1 inhibitor previously referred to as R552 that is being evaluated in an adaptive Phase IIa/IIb clinical trial in up to 380 patients with active moderate to severe rheumatoid arthritis. During the fourth quarter, enrollment in the Phase IIa part of the study was completed, and the trial is ongoing. Now I'll pass the call to Dean to discuss our financials. Dean?