Enhertu’s EU approval: three questions the earnings model cannot answer

Daiichi Sankyo | Tokyo: 4568 | Reviewed 5 November 2026; figure inputs as of 4 November

My starting view

To assess this approval as a business opportunity, I want to know who receives the drug, in what treatment sequence, and when access translates into prescribing. One issue matters particularly: better treatment before surgery can change the market after surgery.

Enhertu links an antibody targeting the cell-surface marker HER2 to the cancer-killing drug DXd. This indication aims to reduce recurrence in patients whose surgical specimens show residual invasive cancer after preoperative treatment. The mechanism and numerical scenarios are in the one-pager below. EU approval announcement

1. Treatment before surgery can reshape the postoperative market

“Preoperative” means before surgery; “postoperative” means afterwards. For an investor, the distinction also determines where the same patient may receive the same drug.

If better preoperative treatment leaves fewer patients with residual invasive disease, fewer meet that requirement for this postoperative indication. The US has also approved a preoperative Enhertu regimen. That is separate from this EU postoperative approval, but it shows why the future patient pathway matters. FDA approval explanation

An important detail is missing from a simple patient-count model: the DB05 registry excludes patients previously treated with Enhertu or another anti-HER2 antibody–drug conjugate. DB05 alone therefore cannot establish the benefit of postoperative Enhertu in patients who already received it before surgery and still have residual disease. DB05 eligibility criteria

I would follow the patient pathway rather than add preoperative, postoperative and metastatic uses as three independent, fixed markets. A smaller postoperative pool could coincide with more preoperative use of Enhertu itself. The implication for the whole company would need a separate assessment. The timing and scale of such changes in Europe have not been established in this model.

2. How much confidence should we place in 50% uptake?

The central case is not a statistically established most-likely forecast. It is a calculation using research-informed conditions because EU-wide treatment pathways and manufacturer net prices are not fully known.

DB05 selected high-risk patients and excluded certain lung conditions, among other criteria. The EU indication does not reproduce the same high-risk restriction. The observed 8.7-point absolute benefit cannot simply be assumed for everyone within the approved population. Recurrence risk and treatment burden will influence actual adoption. DB05 registry, EU indication

Access also varies by country. EMA explains that pricing and reimbursement decisions are made nationally. EU approval does not establish simultaneous access or identical uptake across all 27 member states. EMA on pricing and reimbursement

Changing one assumption illustrates the exposure. Holding everything else at the central case, reducing uptake from 50% to 40% lowers the EPS contribution from about ¥2.8 to ¥2.2. Separately, reducing the residual-disease share from 40% to 30% gives about ¥2.1.

These are my illustrative sensitivities, not simultaneous changes or revised company forecasts. They do not recalculate profits moving into preoperative treatment. I place more weight on finding evidence for these inputs than on making the central estimate look more precise.

3. Read the revenue mix, the costs and the expectations already in place

Growth in European Enhertu sales would not by itself establish that this postoperative indication is succeeding. The regional sales in the reviewed IR materials cover more than this indication. I would look for the company’s explanation of growth and, where available, indication-specific prescribing information. Quarterly reference data

The expense lines also need interpretation. The disclosed accounting includes gross-profit sharing with the partner within selling, general and administrative expenses. Contractual sharing can grow with sales, so I would examine the reason for the cost increase as well as revenue growth. Aggregate expenses cannot establish DB05’s own profit margin. Reference data, page 1, footnote 2

The drug’s earnings contribution is also different from earnings above existing expectations. Clinical results were disclosed in 2025, and Mizuho reportedly raised its DB05 sales forecast before EU approval. At least some analysis of the opportunity therefore existed earlier. Trial results, Traders Web, 26 November 2025

The Mizuho assessment is historical reporting verified in search-retrieved text; the underlying note was not obtained. Matching EU27 indication-level forecasts and the market’s current embedded assumption remain unverified. There is no basis for adding the figure’s full EPS contribution to existing estimates as a fresh approval-driven upgrade.

Here is what would let me update the assessment.

Calculation and source notes

The figure models women in the EU27 under established use in the year ending March 2030. Its eligible population combines European incidence estimates and studies from several countries; it is not a measured EU-wide count. Net pricing, manufacturing margins and additional expense rates include author assumptions. The scenarios are not probability bounds. Approximately 1.82bn shares and ¥180 per euro are fixed references. The additional sensitivities use the same central inputs.

The 10% adjustment for other-indication profit effects in that financial year does not explicitly model individual patient pathways. It is an assumption to revisit, not a precise forecast of profits across preoperative, postoperative and metastatic care. Public prices are distinguished from manufacturer net revenue, and approval milestones from recurring product profits.

This article was prepared with assistance from generative AI.