Korsana Biosciences, Inc.

Paragon Platform Option Agreement

In October 2025, the Company entered into the Platform Option Agreement with Paragon and Parasa (the “Paragon POA”) in connection with the Paragon ADOA. Pursuant to the Paragon POA, the Company will have an exclusive option to enter into either a separate Antibody Discovery and Option Agreement or a separate License Agreement with Paragon and Parasa, enabling the Company with the right to add, remove, or replace specific target combinations and further develop, manufacture and commercialize the resulting antibody transport vehicle compounds.

Following designation of a target combination, the Company may elect their option to enter into a separate Antibody Discovery and Option Agreement or a separate License Agreement with Paragon and Parasa, the terms of which will be finalized in connection with the option exercise. If the Company elects to enter into a License Agreement (a “POA License”), it will be required to makea one-time non-refundable payment to Paragon of $5.0 million for the license option exercise fee. Under any POA License, Korsana would be required tomake one-time, non-refundable milestone payments of up to $41.0 million per product, reduced by 50% for independently developed products directed to the same target combination, and tiered royalty payments in the lowto mid-single digit percentage range based on annual net sales, subject to certain reductions. These payments are intended to fund the research to be performed by Paragon and Parasa under either an Antibody Discovery and Option Agreement or License Agreement. As of June 30, 2026, the Company has not exercised its option and no amounts were expensed related to the Paragon POA during the six months ended June 30, 2026.

The Company will also have an exclusive option to designate up to two additional reserved target combinations. If the Company exercises its option, it will be required to makea one-time non-refundable payment to Paragon of $2.0 million for the additional reserved target option exercise fee. A separate additional reserved target option exercise fee is due and payable to Paragon each time that the Company exercises an additional reserved target option.