Allschwil, Switzerland - March 29, 2019
Idorsia Ltd (SIX: IDIA) today issued the formal invitation to the upcoming Annual General Meeting (AGM) of Shareholders on behalf of the Board of Directors. The meeting to approve the Business Report of the year ending December 31, 2018 will be held on Friday May 3, 2019 at 11.00 CEST at the Congress Center, Messe Basel, Switzerland.

Notes to Shareholders
The invitation will be published in the Swiss Official Gazette of Commerce (Schweizerisches Handelsamtsblatt) and distributed to Shareholders by post on April 10, 2019, and is available, together with the Company's Annual Report and Compensation Report, on www.idorsia.com/agm.

In order to attend and vote at the Annual General Meeting, shareholders must be registered in the company's shareholder register by April 24, 2019 at the latest.

Letter from the Chairman

Dear Shareholders,

It is with great pleasure that I invite you to Idorsia's Annual General Meeting 2019 where we will review the progress made by your company in 2018.

In 2018, Idorsia saw advances on all fronts:

• We advanced our pipeline, bringing four products into Phase 3 development.
• We completed demerger activities, with all core systems now running independently of Actelion.
• We appointed a leader to build our commercial organization, thus taking another step forward towards financial sustainability.
• We strengthened our cash position so as to be able to run our Phase 3 clinical trials and then take strategic decisions on how best to commercialize our assets.

At the upcoming Annual General Meeting, you will have the opportunity to hear more about these achievements and put them into the context of our strategic priorities for building Idorsia into a one of Europe's leading biopharmaceutical companies. You can also find a description of our activities in our Annual Report 2018 at: www.idorsia.com/annual-report.

In preparation for the AGM, I would like to give you some context and background on a few of the items we will be discussing and voting on.

There are going to be some changes to the Board of Directors. David Stout will not be standing for re-election this year, and I would like to take this opportunity to thank David for his valuable contributions to Idorsia. In his place, the Board of Directors proposes Dr. Mathieu Simon for election to the Board. Dr. Simon is a Senior Advisor at Messier Maris & Associés, an advisory M&A firm and a Venture Partner at BB Pureos Bioventures. Dr. Simon has spent his career in the pharmaceuticals industry, serving increasingly senior roles up to CEO and Chairman of the Board. I am sure Dr. Simon will be an important addition to our Board, as we prepare the company for the successful conclusion of the late-stage clinical development of key assets and move closer to bringing our innovation to patients.

Of course, this preparation requires investment. For every Phase 3 program that is in clinical development there are activities on-going across the company to prepare the comprehensive dossier required by health authorities. Preclinical work, such as toxicology studies, clinical pharmacology work, pharmaceutical development and supply chain management to ensure market launch readiness, not to mention the preparation of the scientific material to explain the unique properties of each product to the prescribers.

We are very lucky to have a several assets worthy of our investment and a great team of professionals who know exactly what it takes to register a drug and market it successfully. We must also ensure financial and strategic flexibility, to this end we will be asking you to approve returning our authorized capital to the same level as before we raised additional capital in 2018.

You will also be voting on the 2018 Compensation Report and on the proposed aggregate maximum amounts of compensation for the Board and for Executive Management. More information on this topic is available in the Appendix to this invitation, where you will see that our approach is fully aligned with Idorsia's business strategy and our established compensation principles.

Idorsia really did achieve a lot in 2018, and 2019 will be another exciting year as we move closer to the key results and creating long-term value.

I look forward to welcoming you to Idorsia's Annual General Meeting of Shareholders in May.

Best regards,

Jean-Pierre Garnier
Chairman of the Board of Directors

Agenda for the Annual General Meeting of Shareholders 2019

      1.        Annual Report 2018, Consolidated Financial Statements 2018, Statutory Financial Statements 2018, and Compensation Report 2018

            1.1       Approval of Annual Report 2018, Consolidated Financial Statements 2018, and Statutory Financial Statements 2018

            1.2       Consultative vote on the Compensation Report 2018

      2.        Appropriation of available earnings

      3.        Discharge of the Board of Directors and of the Executive Committee

      4.        Extension and increase of existing authorized share capital

      5.        Board elections

            5.1       Re-election of the Board of Directors

            5.2       Election of a new Director

            5.3       Election of the Chairperson of the Board of Directors

            5.4       Election of the Nominating, Governance & Compensation Committee

      6.        Approval of Board compensation and Executive Committee compensation

            6.1       Approval of Board compensation (Non-Executive Directors) for the 2019-2020 term of office

            6.2       Approval of Executive Committee compensation 2020

      7.        Election of the Independent Proxy

      8.        Election of the statutory auditors

About Idorsia
Idorsia Ltd is reaching out for more - We have more ideas, we see more opportunities and we want to help more patients. In order to achieve this, we will develop Idorsia into one of Europe's leading biopharmaceutical companies, with a strong scientific core.

Headquartered in Switzerland - a biotech-hub of Europe - Idorsia is specialized in the discovery and development of small molecules, to transform the horizon of therapeutic options. Idorsia has a broad portfolio of innovative drugs in the pipeline, an experienced team, a fully-functional research center, and a strong balance sheet - the ideal constellation to bringing R&D efforts to business success.

Idorsia was listed on the SIX Swiss Exchange (ticker symbol: IDIA) in June 2017 and has over 750 highly qualified specialists dedicated to realizing our ambitious targets.

For further information, please contact
Andrew C. Weiss
Senior Vice President, Head of Investor Relations & Corporate Communications
Idorsia Pharmaceuticals Ltd, Hegenheimermattweg 91, CH-4123 Allschwil
+41 (0) 58 844 10 10
www.idorsia.com

The above information contains certain "forward-looking statements", relating to the company's business, which can be identified by the use of forward-looking terminology such as "estimates", "believes", "expects", "may", "are expected to", "will", "will continue", "should", "would be", "seeks", "pending" or "anticipates" or similar expressions, or by discussions of strategy, plans or intentions. Such statements include descriptions of the company's investment and research and development programs and anticipated expenditures in connection therewith, descriptions of new products expected to be introduced by the company and anticipated customer demand for such products and products in the company's existing portfolio. Such statements reflect the current views of the company with respect to future events and are subject to certain risks, uncertainties and assumptions. Many factors could cause the actual results, performance or achievements of the company to be materially different from any future results, performances or achievements that may be expressed or implied by such forward-looking statements. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described herein as anticipated, believed, estimated or expected.