Oncopeptides

Share Issue/Capital Change • Mar 31, 2021

Stockholm, Sweden Press release March 31, 2021

Number of shares and votes in Oncopeptides

Stockholm — March 31, 2021 — Oncopeptides AB (Nasdaq Stockholm, ONCO) today announces that the number of shares and votes in Oncopeptides has changed due to the exercise of warrants under the company's incentive program.

Through the exercise of warrants under the company's incentive program, the number of outstanding shares and votes has increased by 145,140 from 67,939,715 to 68,084,855. The share capital has increased by approximately SEK 16,127 from SEK 7,548,857 to SEK 7,564,984.

For further information, please contact:

Anders Martin-Löf, CFO of Oncopeptides E-mail: anders.martin-lof@oncopeptides.com Telephone: +46 (0) 70 683 79 77

Linda Holmström, Director Investor Relations, Oncopeptides AB E-mail: linda.holmstrom@oncopeptides.com Telephone: + 46 (0) 70 873 40 95

The information in the press release is information that Oncopeptides is obliged to make public pursuant to the Swedish Financial Instruments Trading Act. The information was submitted for publication, through the agency of the contact persons above, on March 31, 2021 at 08.00 (CET).

About Oncopeptides

Oncopeptides is a global biotech company focused on the development of targeted therapies for difficult-to-treat hematological diseases. The lead product candidate melflufen, is a first in class peptide-drug conjugate that targets aminopeptidases and releases alkylating agents into tumor cells. Melflufen is in development as a new treatment for the hematological malignancy multiple myeloma and is being tested in multiple clinical studies including the pivotal phase 2 HORIZON study and the phase 3 OCEAN study. Based on the results from the HORIZON study a New Drug Application has been submitted to the U.S. Food and Drug Administration, FDA, for accelerated approval of melflufen in combination with dexamethasone for treatment of adult patients with triple-class refractory multiple myeloma. The FDA has granted the New Drug Application a priority review with a PDUFA date of February 28, 2021.Oncopeptides´ global Headquarters is in Stockholm, Sweden and the U.S. Headquarters is situated in Boston, Mass. The company is listed in the Mid Cap segment on Nasdaq Stockholm with the ticker ONCO.

More information is available on www.oncopeptides.com.