US-based Spectrum Pharmaceuticals has begun a Phase II clinical trial of its new pan-HER inhibitor, Poziotinib, for patients with HER2-positive metastatic breast cancer.

The open-label trial will involve around 70 patients who have failed at least two prior HER2-directed therapies.

The company noted that Poziotinib has shown a 60% response rate in Phase I patients with breast cancer who had previously failed multiple lines of treatment, including the HER2-directed therapies.

Poziotinib irreversibly blocks signalling through the epidermal growth factor receptor (EGFR, HER) family of tyrosine-kinase receptors, including HER1, HER2, and HER4.

"We believe Poziotinib has the potential to be the best-in-class pan-HER inhibitor."

It also blocks HER receptor mutations, which inhibits the proliferation of tumour cells that overexpress these receptors.

Spectrum Pharmaceuticals chairman and chief executive officer Rajesh Shrotriya said: "We believe Poziotinib has the potential to be the best-in-class pan-HER inhibitor.

"The US Phase II trial was designed on learnings from Hanmi’s Phase I studies, as well as the ongoing Phase II breast cancer trial in Korea.

"The target market for HER2-positive agents is large, and we are encouraged by early data showing that Poziotinib could potentially be another treatment option for patients."

It is reported that mutations or overexpression / amplification of EGFR family receptors have been associated with a number of different cancers, including non-small cell lung cancer (NSCLC), breast cancer and gastric cancer.

At present, poziotinib is being evaluated by Hanmi in several mid-stage trials in different solid tumour indications, including HER2-positive breast cancer.