Scott Koenig
Analyst · Barclays
Thank you, Jim. We are very pleased by the continued progress towards our goal of providing patients with multiple potentially life-changing therapeutics in the pursuit of fighting cancer. At ESMO in September, we presented encouraging preliminary clinical results from the ongoing Phase I study of MGC018, our anti-B7-H3 antibody drug conjugate. In October, we submitted an IND application for MGD024 a next-generation DART molecule targeting CD123 and CD3 for the potential treatment of AML and other CD123 expressing hematological diseases. And finally, the FDA recently approved our GMP manufacturing facility to produce MARGENZA drug substance, representing an important achievement for the company. With that backdrop, let me use this time to walk you through updates on our portfolio of clinical molecules, starting with our molecules targeting B7-H3. Let me first discuss MGC018, our investigational antibody drug conjugate designed to deliver a DNA escalating duocarmycin cytotoxic payload to tumors expressing B7-H3. MacroGenics presented an encouraging update of clinical data from the ongoing Phase I study of MGC018 in patients with advanced solid tumors in a poster presentation at ESMO in September. The safety analysis included all enrolled patients with the activity analysis focused on the metastatic castration-resistant prostate cancer or MCRPC and non-small cell lung cancer expansion cohorts, as enrollment continues in the other 3 tumor cohorts. As of August 16, 2020 data cutoff, the preliminary results demonstrated a PSA reduction of 50% or greater and 21 of 39 or 54% of patients with MCRPC. Antitumor activity was observed in 10 of 16 or 63% of resist evaluable patients and 4 of 16 or 25% of patients achieved a partial response, including 2 and 2 unconfirmed partial responses. As presented at ESMO, preliminary results in the non-small cell lung cancer cohort expansion demonstrated antitumor activity in 13 of 16 or 81% of patients with measurable disease who had their first 9-week imaging results available, including 4 of 16 or 25% of patients with unconfirmed responses. The adverse events for all 86 patients in the dose expansion was reported to be manageable and included, most notably, hematologic toxicity and low-grade fatigue, skin toxicities and infusions. Overall, we continue to remain pleased and encouraged by the growing data from our ongoing study of MGC018. Following ESMO, we had multiple discussions with practicing prostate cancer physician researchers, and we look forward to sharing our future development plans for MGC018 in MCRPC during the first quarter of next year. In addition, enrollment in the MGC018 Phase I study is ongoing in the triple-negative breast cancer, squamous cell carcinoma of the head and neck and melanoma cohorts. We expect to provide clinical updates on multiple expansion study cohorts in the first half of next year. In addition to monotherapy-based studies, we anticipate commencing a combination study of MGC018 with one of our PD-1-based product candidates in the first half of next year. Another of our investigational molecules exploiting the overexpression of B7-H3 in solid tumors is enoblituzumab, an Fc-engineered antibody created using our Fc optimization platform. In March, we initiated a combination study of enoblituzumab in a chemotherapy-free regimen in frontline squamous cell carcinoma of the head and neck with either tebotelimab for patients who are PD-L1 negative or with retifanlimab in patients who are PD-L1 positive. Enrollment in this study continues to progress across sites in the United States, Europe and Australia. In September, our partner, I-Mab Biopharma, announced that its IND to initiate a Phase II trial of enoblituzumab in combination with pembrolizumab in patients with select solid tumors was accepted in China, which triggered a net $4.5 million milestone payment to MacroGenics. Next, let me discuss our efforts to bring products to market to help treat patients with acute myeloid leukemia or AML and our investigational bispecific CD123 x CD 3 DART molecules. We continue to enroll the single-arm clinical study to evaluate flotetuzumab in patients with refractory AML, and we anticipate providing further updates on the clinical development of flotetuzumab in 2022. In addition, I'm very pleased to share that we recently submitted an IND application to the FDA for MGD024, our next-generation CD123 x CD3 DART molecule that we intend to study in patients with relapsed or refractory hematologic malignancies. The IND application is pending clearance by the FDA. MGD024 incorporates a CD3 component designed to minimize cytokine release syndrome, while maintaining antitumor cytolytic activity, along with an Fc domain to prolong circulating half-life and permit intermittent dosing. We expect to present preclinical MGD024 data at ASH in December. Next up, let me walk you through our PD-1-based assets. Tebotelimab is our investigational bispecific PD-1 x LAG-3 DART molecule. Tebotelimab blocks the binding of T cells expressing PD-1 and LAG-3 to their ligands and allows for the reactivation of exhausted T cells and enhancement of immune capacity against tumors. Tebotelimab has demonstrated synergistic T cell activation in vitro, superior to that seen with other PD-1 and LAG-3 combinations with PD-1 or LAG-3 as single agents. We are currently evaluating tebotelimab in patients as both monotherapy, as well as in combination with other agents. Zia Lab, our partner in Greater China, expanded the Phase Ib/II study of tebotelimab in combination with a PARP inhibitor, niraparib, into new indications in Greater China, including gastric cancer, triple-negative breast cancer and biliary tract cancer. In addition, Zia Lab enrolled the first patient in the endometrial cancer cohort in October 2021. Next, MGD019 is our investigational bispecific checkpoint DART molecule that targets PD-1 and CTLA-4. We are conducting a Phase I dose expansion study in cohorts of patients with microsatellite stable colorectal cancer, checkpoint-naive, non-small cell lung cancer, MCRPC and melanoma. We look forward to providing an update on the study next year. Let me next turn to retifanlimab, the investigational anti-PD-1 antibody that we licensed to Incyte. Incyte is exploring development of retifanlimab, as monotherapy and potentially registration-enabling studies in patients with anal cancer, MSI-high endometrial cancer, Merkel cell carcinoma and lung cancer. In addition, Incyte is evaluating the molecule in combination with other assets in their immuno-oncology portfolio. At the 2021 Society for Immunotherapy of Cancer or SITC, virtual meeting next week. Incyte will present clinical results in poster presentations from both a Phase 2 study of retifanlimab in patients with advanced or metastatic Merkel cell carcinoma, and a tumor-specific expansion cohort study in patients with the current MSI-high or deficient mismatch repair recurrent endometrial cancer. Next, our second investigational ADC, IMGC0936, which targets ADAM9 is being advanced under a co-development agreement with Immunogen. Under our 50-50 collaboration immunogen is leading clinical development, and they have indicated they anticipate disclosing initial data from a Phase 1 study in multiple solid tumors in 2022. Last but not least, I will provide an update on margetuximab. We have been evaluating margetuximab in the Phase 2/3 MAHOGANY study in patients with advanced gastric and gastroesophageal junction cancer. This trial consists of 2 modules designed to evaluate margetuximab as an investigational agent in combination with a checkpoint inhibitor with or without chemotherapy, as a potential first-line treatment for patients with advanced or metastatic HER2-positive GC or gastroesophageal junction cancers. At ESMO in September, clinical results from Cohort A Part 1 of the Phase 2/3 MAHOGANY study of margetuximab in combination with retifanlimab in patients with advanced gastric and gastroesophageal junction cancer were presented. 21 of 40 or 53% of resistant valuable patients in MAHOGANY Cohort A achieved confirmed responses by independent review. Although the number of confirmed responses exceeded the prespecified futility boundary for the trial after further evaluation of company resources and priorities, we have decided to discontinue enrollment of Cohort A based on a number of factors, including the prioritization of our other product candidates given the competition in this indication and the accelerated approval of combination therapy with pembrolizumab. Our partner for margetuximab in Greater China, Zia Lab, continues to enroll patients in Cohort B. Also in September, the company announced final overall survival analysis from the Phase 3 SOPHIA study, which did not demonstrate a statistically significant advantage for MARGENZA plus chemotherapy over trastuzumab plus chemotherapy in patients with HER2-positive metastatic breast cancer. We plan to present these results at the San Antonio Breast Cancer Symposium in December. In addition to the results from the intent-to-treat population our prespecified non-alpha allocating analysis of CD16A genotyping in the trial showed a numerical OS advantage in favor of margetuximab in F homozygous patients and a numerical OS advantage in favor of trastuzumab in V homozygous patients. With regard to margetuximab in metastatic breast cancer, recall that MARGENZA was launched in mid-March in coordination with our commercial partner, EVERSANA. MARGENZA is approved in combination with chemotherapy for the treatment of adult patients with metastatic HER2-positive breast cancer who have received 2 or more prior anti-HER2 regimens, at least one of which was for metastatic disease. In October, Zai Lab announced that its bridging study of margetuximab plus chemotherapy in advanced previously treated HER2-positive breast cancer met its primary endpoint with acceptable safety and tolerability. The study showed that efficacy of this combination in Chinese patients was consistent with that seen in the global population in the SOPHIA trial. Zia Lab has indicated that it anticipates submitting a BLA in China for pretreated metastatic HER2-positive breast cancer by approximately year-end 2021. We continue to believe patients may benefit from MARGENZA, as another marketed cancer therapy option. As reported, net sales were $3.6 million from MARGENZA in the third quarter. Given the competitive realities that have taken place in the HER2-positive breast cancer market, including multiple new approvals, we continue to have modest expectations for MARGENZA sales. We expect to provide MARGENZA sales guidance after the product has been on the market for at least a year. Finally, we recently received U.S. FDA approval to manufacture MARGENZA drug substance at our GMP manufacturing facility in Rockville, Maryland. The supplemental BLA approval for MARGENZA represents another important achievement for MacroGenics. We look forward to continuing to build momentum, and advancing our pipeline of innovative product candidates throughout 2021 and into 2022. We would now be happy to open the call for questions. Operator?