Starpharma Holdings (ASX:SPL) said its DEP HER2-targeted radiotherapy candidate showed "encouraging anti-tumor activity" in support of a planned first-in-human phase one clinical study in the second half of the year, according to a Thursday filing with the Australian bourse.

In preclinical HER2-positive cancer models, the radiotherapy candidate demonstrated "strong" tumor uptake and retention, low kidney accumulation, and short blood circulation time, the company said.

The candidate also showed a statistically significant survival benefit, with the effects comparable to the already approved Enhertu cancer drug in those models, per the filing.

Phase one preparations are well advanced, and feedback from drug regulators supports the proposed development pathway, Starpharma said.

The company's shares gained 1% in recent Thursday trade.