Dose escalation for HPN217 (BCMA TriTAC) Phase 1/2 clinical trial Ongoing
Relapsed/refractory multiple myeloma patients (N=37) have been treated across 9 fixed dose cohorts of 5 to 2860 µg/week, and 1 step dose cohort of 1620 (priming) and 3240 (target) µg/week reflecting rapid dose expansion since the trial began. HPN217 has been well tolerated, with one DLT, Grade 4 AST which resolved, as of the November 10, 2021 data cutoff date.
The ASH poster presentation, included the following observations:
| | • | | Encouraging clinical activity in higher dose cohorts including a 63% ORR and 88% DCR reported in the 2150 µg/week cohort with 8 disease evaluable patients with R/R MM, including one minimal residual disease (MRD) negative, stringent CR. |
| | • | | HPN217 shows tolerable safety profile with cytokine release syndrome (all Grade 1 or 2) observed in 9 of 37 patients (24%) |
| | • | | Patient enrollment and dose escalation is ongoing to define the RP2D and MTD |
| | • | | Introduction of step dose regimens has allowed for the administration of higher target doses. |
Dose escalation for HPN328 (DLL3 TriTAC) Phase 1/2 clinical trial making rapid progress. Fifteen patients have been enrolled in dose cohorts ranging from 15 µg to 7200 µg per week in both fixed and step dose cohorts administered once weekly by intravenous infusion. Fifteen patients with a median of 2 lines (range 1 to 5) of prior therapy have been enrolled and eligible patients include small cell lung cancer patients who have relapsed after platinum chemotherapy and patients with other malignancies with high grade neuroendocrine tumors associated with DLL3 expression. HPN328 has been well tolerated with Grade 1-2 CRS reported in 33% of patients, no DLTs observed and MTD has not been reached. Among four patients with small cell lung cancer receiving the two highest doses tested to date, 1215 µg fixed dose and 3600-7200 µg step dose, three had target lesion reduction, including 1 confirmed RECIST partial response. The patient with a cPR experienced a target lesion reduction of 53% at week 10. Presentation of initial interim clinical data is planned for 2022.
IND-enabling studies for HPN601 (EpCAM ProTriTAC) are progressing as planned. HPN601 is the first conditionally active T cell engager based on the ProTriTAC platform. EpCAM is expressed in a broad range of solid tumors, including gastrointestinal cancers, potentially enabling HPN601 to address multiple indications with high unmet medical need. By the end of 2022, an IND submission for HPN601 is expected as well as identification of a second IND candidate from the ProTriTAC platform.
Harpoon’s T cell engager platforms, TriTAC, ProTriTAC, and TriTAC XR, are designed to mitigate different target toxicities across a range of disease indications, including solid and hematologic malignancies.
Next generation T cell engager platforms advancing. Harpoon continues to discover new technologies to improve the therapeutic application of T cell engagers. We recently introduced the TriTAC XR platform, which is designed to minimize on-target cytokine release syndrome. Nomination of an IND candidate from the TriTAC XR platform is also expected by the end of 2022.
Conference Call and Webcast Today
Harpoon’s management will host a webcast and conference call at 4:30 p.m. ET / 1:30 p.m. PT on Monday, December 13, 2021 to review the data presented at ASH and provide an update on its other pipeline programs. The live call may be accessed by dialing 866-951-6894 for domestic callers or 409-216-0624 for international callers and using conference ID # 2760075.
A live webcast of the call will be available from the Events and Presentations section of the company’s website at https://ir.harpoontx.com/events-and-presentations and will be archived there shortly after the live event.
