Arix Bioscience (AIM:ARIX ) noted that its portfolio company, Harpoon Therapeutics, has dosed its first patient with HPN217 in a clinical trial focused on relapsed, refractory multiple myeloma (RRMM).

Arix holds a 12.1% stake in Harpoon which was valued at £29.7 million as at 30 June 2019.

HPN217, Harpoon’s third product candidate to enter the clinic, is being developed under a global license and option agreement with AbbVie (NYSE:ABBV).

The company told investors on Monday that the dosing of a first patient in a phase 1/2 clinical trial has now triggered a $50 million milestone payment to Harpoon. 

Specifically, HPN217 targets B-cell maturation antigen (BCMA), a well-validated antigen expressed on malignant multiple myeloma cells. 

Shares in Arix Bioscience were trading flat at 85p during Monday trading.

The group said it is based on Harpoon’s proprietary Tri-specific T cell Activating Construct (TriTAC™) platform designed to recruit a patient’s own immune cells to destroy tumours.

Dr Gerald McMahon, President and CEO of Harpoon, said the clinical trial represented “another significant milestone” and was demonstrative of “outstanding progress” for the group’s oncology pipeline.

The group said its first patient was treated at Colorado Blood Cancer Institute and the Sarah Cannon Research Institute at HealthONE’s Presbyterian St. Luke’s Medical Center. 

“The $50 million milestone payment adds additional financial resources to support the HPN217 program and other development activities that we are conducting,” McMahon added.

“Therapeutic choices for patients with RRMM are limited, and there is a need for additional therapeutic options,” said Natalie Sacks, Chief Medical Officer of Harpoon.

Sacks added that non-clinical data suggests that HPN217 has substantial anticancer activity and provides a motive to investigate its potential as an effective immunotherapy for RRMM.

Harpoon also expects to report phase 1 data from its HPN424 metastatic castration resistant prostate cancer study in the first half of 2020.

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