Japanese pharmaceutical company Eisai has agreed to transfer the rights to receive royalties for sales of tazemetostat outside Japan to US-based Royalty Pharma.

Discovered by Epizyme, tazemetostat is an investigational, oral, small-molecule EZH2 inhibitor intended for the treatment of cancer patients. EZH2 is involved in cell proliferation, as well as carcinogenesis.

As part of an agreement with Epizyme in 2015, Eisai is responsible for carrying out development and commercialisation of the drug in Japan, as well as paying royalties on sales in the country to Epizyme.

Epizyme holds rights for tazemetostat outside Japan and will pay to Eisai select development and regulatory milestones, along with royalties on net sales in all regions outside the country.

Under the terms of the latest agreement, Eisai will transfer its rights for royalties on sales outside Japan to Royalty Pharma.

In turn, Eisai will obtain $110m in upfront payments and is eligible for up to an additional $220m, contingent on marketing approvals for the drug in the US for some indications.

The company is currently assessing tazemetostat in Phase II clinical trials for B-cell non-Hodgkin’s lymphoma in Japan.

In a statement, Eisai said: “By the effective use of management resources including the funds obtained through this agreement, Eisai will accelerate to discover the new medicines based on the cutting-edge cancer research, as it seeks to contribute further to addressing the diverse needs of, and increasing the benefits provided to, patients with cancer, their families and healthcare providers.”

Separately, Epizyme entered agreements with Royalty Pharma and its affiliate Pharmakon Advisors.

Royalty Pharma will make a $100m upfront payment for shares of Epizyme common stock for $15 per share.

Furthermore, Epizyme also gets an 18-month option to divest an additional $50m of its common stock to Royalty Pharma, which holds a three-year option to buy another 2.5 million shares of Epizyme stock at $20 per share.