AstraZeneca Plc (AZN) had a good couple of days this week, landing two significant regulatory approvals that expand treatment options for cancer and autoimmune disease patients.

The FDA approved AstraZeneca and Daiichi Sankyo's Enhertu (trastuzumab deruxtecan) combined with pertuzumab on Monday for adult patients with unresectable or metastatic HER2-positive breast cancer. This marks the drug's entry into the first-line treatment setting for this specific cancer type.

Impressive Trial Results

The approval rode on Priority Review and Breakthrough Therapy Designation from the FDA, backed by results from the DESTINY-Breast09 Phase 3 trial. The numbers tell a compelling story: Enhertu plus pertuzumab reduced the risk of disease progression or death by 44% compared to the standard regimen of taxane, trastuzumab, and pertuzumab.

Median progression-free survival reached 40.7 months with the Enhertu combination versus 26.9 months for the standard treatment. That's nearly 14 additional months before disease progression. The benefit held consistent across different patient subgroups, suggesting broad applicability.

Financial Implications

This approval triggers a $150 million milestone payment from AstraZeneca to Daiichi Sankyo for the first-line HER2-positive breast cancer indication. It's worth noting that Daiichi Sankyo continues to recognize all U.S. sales of Enhertu, even as both companies share development responsibilities.

EU Approves Lupus Pen Device

In separate news, the European Commission approved AstraZeneca's Saphnelo (anifrolumab) on Tuesday as a pre-filled pen for subcutaneous self-administration. The approval applies to adult patients with systemic lupus erythematosus who are on standard therapy.

The green light followed a positive opinion from the Committee for Medicinal Products for Human Use and draws on Phase 3 TULIP-SC trial data. That study showed subcutaneous Saphnelo delivered statistically significant and clinically meaningful reductions in disease activity compared to placebo in patients with moderate-to-severe, active, autoantibody-positive lupus.

The Royalty Arrangement

Here's where it gets interesting from a business perspective. AstraZeneca acquired global rights to Saphnelo through a licensing and collaboration deal with Medarex back in 2004. When Bristol-Myers Squibb & Co (BMY) acquired Medarex in 2009, Medarex's option to co-promote the product expired.

Under the terms of that original agreement, AstraZeneca pays Bristol-Myers low- to mid-teens royalties on Saphnelo sales, with the exact percentage varying by geography. So even though Bristol-Myers isn't actively involved in marketing, it still gets a piece of every sale.

AstraZeneca shares were down 1.03% at $90.62 at the time of publication on Tuesday.