Sutro Biopharma, Inc. announced that its research collaborators presented data on anti-leukemic activity from the compassionate use of luveltamab tazevibulin (luvelta), a novel folate receptor-a (FR-a) targeting ADC, in pediatric patients with relapsed/refractory CBFA2T3-GLIS2 (CBF/GLIS) acute myeloid leukemia (AML), commonly known as RAM phenotype AML. Data demonstrated that treatment with luvelta produced meaningful clinical responses, including complete remission (CR); and prolongs overall survival (OS) enabling some patients to receive potentially curative therapies such as hematopoietic stem cell transplant. These patients were treated under the single patient IND mechanism.

These data were featured in a poster presentation at the 65th American Society of Hematology Annual Meeting and Exposition (ASH 2023) in San Diego, CA. CBF/GLIS subtype AML is a rare and highly lethal form of leukemia found exclusively in infants and young children, with the average age of onset at 18 months. There are no therapies specifically approved to target this form of leukemia and it is resistant to conventional chemotherapy, with an induction failure rate of over 80%.

Due to a lack of effective treatment, children diagnosed with the disease have a dismal two-year survival rate of 15%. Recent studies have shown that FOLR1, which encodes for FolRa, is silent in normal hematopoiesis, but is uniquely induced by the CBF/GLIS fusion. Under compassionate use, 25 pediatric patients with relapsed/refractory CBF/GLIS subtype AML were treated with luvelta at doses up to 4.3 or 5.2mg/kg every two to four weeks for a median duration of 15.9 weeks (3-73.1), with the majority of patients receiving at least five doses (68%).

Of the 25 treated patients, 19 had =5% blasts (morphologic disease, or MD) and 8 had <5% blasts (sub-morphologic disease, or SMD)5. Collective results show that treatment with luvelta produced clinically meaningful and durable responses across a broad range of patients in various settings including in patients with or without prior stem cell transplant and in monotherapy or in combination with cytotoxic therapy. These data were generated by the treating physicians and collected and enabled for presentation by Sutro.