Harpoon Therapeutics Provides Progress Update for TriTAC® Clinical Programs and ProTriTAC™ Platform
- Three TriTAC clinical programs (HPN424, HPN536 and HPN328) have shown tumor size reductions or stable disease, and meaningful treatment duration
- All four clinical programs demonstrate half-life extension, target engagement and T cell activation
- Cytokine release syndrome observed and manageable, with low incidence of severe CRS
- Management to host webcast and conference call to review the interim data presented at ASCO and provide a pipeline update today at
4 p.m. ET/ 1 p.m. PT
“We are excited by the clinical data emerging from our four TriTAC programs that are showing tumor size reductions or stable disease, meaningful treatment duration, clinical activity, target engagement, extended half-life, and manageable safety and tolerability profiles in the heavily pretreated patient populations,” stated
“The clinical signals observed in the HPN424 trial and the unconfirmed partial response in the recently initiated HPN328 trial are very encouraging,” said
Dose escalation and step dosing for HPN424 Phase 1/2a clinical trial continuing.
- Eight patients most recently enrolled in this cohort were treated with the same modified step dose regimen. Preliminary data from these patients include 3/8 (38%) with PSA declines that occur early in the course of treatment.
- For the total 19 patients enrolled in this cohort, 4/19 showed PSA declines, including two patients with PSA30.
The ASCO poster presentation, included the following observations:
- Antitumor activity includes a confirmed PR per RECIST, PSA declines and CTC reductions.
- Fifteen of 74 (20%) pts with >1 post-baseline value had PSA decreases from baseline ranging from -2% to -76%, including 4 pts with PSA50 response and 2 pts with PSA30 response
- Treatment duration > 24 weeks observed in 15 of 74 (20%) pts, including 8 of 17 (47%) chemo-naïve patients
- Reduction in CTCs was seen in 36 of 64 (56%) patients with available baseline and on-treatment CTC counts
- CRS has been transient and manageable with 4% of patients experiencing Grade 3 CRS
- CRS and transaminitis events observed most often in Cycle 1, with diminished frequency and severity in subsequent cycles
- Introduction of step dose regimens has allowed for the administration of higher target doses, currently at 300ng/kg
HPN536 (mesothelin TriTAC) Phase 1/2a clinical trial continues dose escalation. Dosing has occurred across 10 fixed-dose cohorts of 6 to 560ng/kg and three step dose cohort up to 1200ng/kg, with total enrollment of 60 patients. Tumor types treated include late-stage ovarian (47%), pancreatic (40%) and peritoneal and pleural mesothelioma (13%) cancers. Pharmacokinetic analysis shows median half-life of more than 70 hours for HPN536. Among the relapsed/refractory ovarian cancer patients with at least one post-baseline scan, 11 of 20 (55%) patients showed stability of target lesions, including three patients with target lesion shrinkage. In addition, five of 27 (19%) ovarian cancer patients had a duration of treatment of greater than 24 weeks. As of
Dose escalation for HPN217 (BCMA TriTAC) Phase 1/2 clinical trial making good progress. Relapsed/refractory multiple myeloma patients (N=20) have been treated across eight fixed dose cohorts of 5 to 2150 µg weekly, reflecting rapid dose expansion since the trial began. HPN217 has been well tolerated, and no DLTs have been observed as of the
Dose escalation for HPN328 (DLL3 TriTAC) Phase 1/2 clinical trial initiated in late 2020 and has shown rapid progress. The first single patient cohort began with a flat dose of 15µg of HPN328 administered once weekly by intravenous infusion and has proceeded to the fourth cohort at a dose of 405µg. Eligible patients include small cell lung cancer patients who have relapsed after platinum chemotherapy and patients with other tumors associated with DLL3 expression. An unconfirmed partial response has been observed for one patient with small cell lung cancer from the 45µg dose cohort. Presentation of initial interim data is planned for the second half of 2021.
IND-enabling studies for HPN601 (EpCAM ProTriTAC) are progressing as planned. HPN601 is a 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.
Conference Call and Webcast Today
Harpoon’s management will host a webcast and conference call at
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.
Harpoon Therapeutics is a clinical-stage immunotherapy company developing a novel class of T cell engagers that harness the power of the body’s immune system to treat patients suffering from cancer and other diseases. T cell engagers are engineered proteins that direct a patient’s own T cells to kill target cells that express specific proteins, or antigens, carried by the target cells. Using its proprietary Tri-specific T cell Activating Construct (TriTAC®) platform, Harpoon is developing a pipeline of novel TriTACs initially focused on the treatment of solid tumors and hematologic malignancies. HPN424 targets PSMA and is in a Phase 1/2a trial for metastatic castration-resistant prostate cancer. HPN536 targets mesothelin and is in a Phase 1/2a trial for cancers expressing mesothelin, initially focused on ovarian and pancreatic cancers. HPN217 targets BCMA and is in a Phase 1/2 trial for relapsed, refractory multiple myeloma. HPN328 targets DLL3 and is in a Phase 1/2 trial for small cell lung cancer and other DLL3-associated tumors. Harpoon has also developed a proprietary ProTriTAC™ platform, which applies a prodrug concept to its TriTAC platform to create a therapeutic T cell engager that remains inactive until it reaches the tumor. For additional information about
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Source: Harpoon Therapeutics