Report on the review of condensed consolidated interim financial statements

Introduction

We have reviewed the accompanying condensed consolidated balance sheet of BB Biotech AG as of June 30, 2025 and the related condensed consolidated statements of income, changes in equity and cash flows for the six-month period then ended, and a summary of significant accounting policies and other explanatory notes. The Board of Directors is responsible for the preparation and presentation of this interim financial information in accordance with International Accounting Standard 34 «Interim Financial Reporting» and article 14 of the Directive on Financial Reporting of the SIX Swiss Exchange. Our responsibility is to express a conclusion on this interim financial information based on our review.

Scope of Review

We conducted our review in accordance with the Swiss Auditing Standard 910 (SAS 910) «Engagements to Review Financial Statements» and the International Standard on Review Engagements (ISRE) 2410 «Review of interim financial information performed by the independent auditor of the entity». A review of interim financial information consists of making inquiries, primarily of persons responsible for financial and accounting matters, and applying analytical and other review procedures. A review is substantially less in scope than an audit conducted in accordance with International Standards on Auditing and consequently does not enable us to obtain assurance that we would become aware of all significant matters that might be identified in an audit. Accordingly, we do not express an audit opinion.

Conclusion

Based on our review, nothing has come to our attention that causes us to believe that the accompanying condensed consolidated interim financial information for the six months ended June 30, 2025 are not prepared, in all material respects, in accordance with International Accounting Standard 34 Interim Financial Reporting and article 14 of the Directive on Financial Reporting of the SIX Swiss Exchange.

Deloitte AG

Zurich, 22 July 2025

Deloitte AG, Pfingstweidstrasse 11, CH-8005 Zurich
Phone: +41 (0)58 279 60 00, Fax: +41 (0)58 279 66 00, www.deloitte.ch