UK pharma AstraZeneca has sold the US and Canadian rights for one of its oldest breast cancer drugs to TerSera Therapeutics in a deal worth up to $320 million.

An initial $250 million will be paid upon completion of the deal by US-based TerSera, as well as an additional $70 million in milestone payments and quarterly royalties of around 15% of product sales.

Zoladex (goserelin) – an injectable luteinising hormone-releasing hormone agonist – was first approved in the US in 1989 for the treatment of prostate cancer. It has since earned approvals for breast cancer and certain benign gynaecological disorders.

As part of the deal, AstraZeneca will manufacture and supply Zoladex to TerSera.

“This agreement allows us to retain a significant share of the value of Zoladex in the US and Canada, while concentrating our resources on our innovative new oncology medicines,” said Mark Mallon executive vice president, global product and portfolio strategy at AstraZeneca. “It also ensures patients have continued access to Zoladex, with TerSera’s dedicated focus helping to expand the potential of this important medicine.”

The sale of Zoladex’s rights is the latest by AstraZeneca which has been busy shedding products it no longer sees as a priority. The funds accrued are intended to cover a period of slow income while the company waits for approvals for some of its newer candidates.

One of its most promising candidates is durvalumab – a PD-L1-targeting immunotherapy – which recently posted positive results in a phase 1/2 trial in the treatment of metastatic urothelial cancer.

In 103 patients, the drug achieved an objective response rate of 20.4% and a median overall survival of 14.1 months.

AstraZeneca is continuing to test durvalumab in combination with tremelimumab and as a first-line monotherapy in bladder cancer in its phase 3 DANUBE trial, according to David Berman, head of oncology at AZ’s MedImmune unit.

The company has forecast peak sales for durvalumab of $6.5 billion.