Netherlands-based Synthon Biopharmaceuticals (Synthon) has dosed first patients in a Phase I trial of its investigational anti-HER2 antibody-drug conjugate (ADC), SYD985, to treat metastatic solid tumours.

SYD985 is a HER2-targeting ADC based on trastuzumab and the company’s cleavable linker-duocarmycin (vc-seco-DUBA) payload.

The trial is enrolling patients at leading European oncology centres including Radboud University Medical Center in the Netherlands, the Jules Bordet Institute in Belgium and the Institute of Cancer Research at The Royal Marsden Hospital in the UK.

"Entering this phase of clinical evaluation is another significant development milestone for SYD985."

Around 76 patients are expected to be enrolled in the two-part Phase I trial, while more centres will be added in 2015.

In the dose escalation part of the trial, safety and efficacy of SYD985 will be evaluated in patients with locally advanced or metastatic solid tumours of any origin, while in the expanded cohort part, only patients with breast and gastric cancer will be enrolled.

The expanded groups will include patients currently indicated for HER2-targeted treatment as well as patients with HER2 2+ and HER2 1+ breast cancer for whom there currently is no effective anti-HER2 therapy available.

Synthon CEO Jacques Lemmens said: "Entering this phase of clinical evaluation is another significant development milestone for SYD985.

"The dose-escalation part of the trial will determine the start of expanded patient cohorts to further evaluate safety and explore preliminary efficacy of this new and promising ADC."

"We believe SYD985 has the potential to at least double the current breast cancer population eligible for HER2-based ADC treatment. If successful, it could provide new treatment options for cancer patients with a high unmet medical need, including triple negative breast cancer patients."

SYD985 is the most advanced candidate in the company’s ADC portfolio and it has showed unprecedented anti-tumour activity in preclinical breast and gastric cancer models with low expression of HER2 (HER2 2+ and HER2 1+).