Shattuck Labs, Inc. announced the presentation of additional data from the Phase 1B dose expansion clinical trial of SL-172154 with AZA in frontline HR-MDS and TP53m AML patients. These data will be featured in a poster presentation at the EHA 2024 Congress, being held June 13-16, 2024, both virtually and in Madrid, Spain. Key Takeaways from Phase 1B Trial of SL-172154 in Frontline HR-MDS and TP53m AML, Interim efficacy as of February 1, 2024 observed for SL-172154 in combination with AZA in frontline HR-MDS and TP53m AML.

EHA poster presentation to include additional data from the next planned cutoff in the second quarter of 2024. HR-MDS: In 23 evaluable patients (20 had TP53m, 21 had complex karyotype, and seven had therapy-related MDS), the objective response rate (ORR) was 65%. Nine patients achieved a CR within 16 weeks as the median time to CR.

None of the patients with CR progressed as of the data cutoff. 16 patients were still undergoing treatment. TP53m AML: In 14 evaluable patients (11 of whom had secondary AML) the ORR was 36%.

A total of 21 patients will be included in the final pre-conference data cutoff. Two patients achieved a CR, the median time to CR was 8.7 weeks. Another patient achieved a CR with incomplete hematologic recovery and two patients achieved a partial response.

None of the responders progressed as of the data cutoff. Four responders (one CR, one CRi, two PR) were taken to hematopoietic cell transplantation (HCT), Six patients were still undergoing treatment, including one patient in CR. Median duration of response and overall survival has not been reached in both HR-MDS and TP53m AML as of the data cutoff date.

Safety: SL-172154 had an acceptable safety profile: Infusion-related reactions (IRRs) were the most common SL-172154 related treatment-emergent adverse events (TEAEs). IRR was reported in 18 patients (46%); all were Grade 1 and 2 except for two Grade 3 events. Other SL-172154 related TEAEs (>=10%) were fatigue in five patients (13%) and hypokalemia in four patients (10%).

Cytokine release syndrome was reported in two patients with HR-MDS (Grade 2 and Grade 3, respectively). 11 patients (28%) experienced at least one Grade 3/4 SL-172154 related TEAE, with fatigue, febrile neutropenia, and IRR as the most common (in two patients each). Two patients had drug discontinuation that were possibly related to SL-172154: one patient had a Grade 4 event of myocardial infarction, and one patient had a Grade 5 event of cardiac arrest.

Both patients had a history of significant cardiovascular disease, adverse risk factors and other comorbidities.