Kymab Group Ltd: Kymab Presents Update on Lead Immunocytokine Program KY1043 at Society of Immunotherapy for Cancer 34th Annual Meeting

Kymab Presents Update on Lead Immunocytokine Program KY1043 at Society of Immunotherapy for Cancer 34^th Annual Meeting

• KY1043, a bifunctional, PD-L1-based, IL-2Ra (CD25)-directed immunocytokine stimulates potent anti-tumor responses in vivo leading to complete regression in established tumor models
• Expanding data set continues to provide evidence for a dual mechanism-of-action of KY1043 in vitro and in vivo
• Development activities, including regulatory-enabling toxicological studies, are in progress

Cambridge, UK; November 8, 2019: Kymab, a clinical-stage biopharmaceutical company developing antibody-based therapeutics, will today present a poster detailing an expanding body of evidence for the activity of the company's novel immunocytokine, KY1043. The poster will be presented at the Society of Immunotherapy for Cancer (SITC) 34^th Annual Meeting being held today at the Gaylord National Hotel and Convention Center, National Harbor, Fort Washington, Maryland, United States.

KY1043 is a novel, fully-human, PD-L1-based, IL-2Ra (CD25)-directed immunocytokine that is designed to both inhibit the interaction between PD-L1 and the T cell checkpoint receptor PD-1 and stimulate T cells via interaction of a mutated form of IL-2 that preferentially activates antigen experienced T cells to promote the immune response against tumors.

Data presented in the SITC poster demonstrate that KY1043 retains the ability to effectively inhibit PD-1/PD-L1 interaction and binds preferentially to the IL-2Ra (CD25)-containing high-affinity trimeric IL-2Rabg receptor present on antigen-experienced and activated T cells as well as on regulatory T cells (Treg). In vitro, KY1043 increases antigen-specific T cell-mediated killing of tumor cells. In vivo, KY1043 administration produces profound tumor growth suppression in an established MC38 tumor model, leading to the regression of tumors in a dose-dependent manner. Mice treated with KY1043 are resistant to subsequent tumor challenge, indicating the potential for long-term anti-tumor memory responses. Mechanism-of-action studies indicate that while Treg cells are increased in the periphery as expected, in the tumor CD8 effector cells are increased without a concomitant increase in intratumoral Treg.

"Our preclinical studies show that targeting PD-L1 and IL-2Ra with KY1043 is a valid approach for inducing a strong anti-tumor immune response," said Sonia Quaratino, M.D., Ph.D., Chief Medical Officer of Kymab. "Our team is now working on bringing this novel therapy to the clinic."

The poster can be viewed during SITC in the following session:

Title: KY1043, a novel PD-L1 IL-2 immunocytokine directed towards CD25, delivers potent anti-tumour activity in vitro and in vivo

Presenter: Cassie Van Krinks

Location: Poster Hall (Prince George AB)

Poster board #: P625

Date and Time: Friday 8^th November, 12.30-2:00 p.m. and 6.30 and 8:00 p.m. EDT

##ENDS###

NOTES TO EDITORS

About KY1043

KY1043 is a novel immunocytokine based on a fully-human PD-L1 antibody discovered by Kymab. KY1043 a bi-functional PD-L1-based IL-2Ra (CD25)-directed immunocytokine and is designed to both inhibit the interaction between PD-L1 and the T cell checkpoint receptor PD-1 and stimulate T cells via interaction of a mutated form of IL-2 that preferentially activates antigen-experienced T cells to promote the immune response against tumors.

KY1043 has been investigated in highly illustrative in vitro and syngeneic models. In vitro, KY1043 increases antigen-specific T cell-mediated killing of tumor cells. In vivo, KY1043 administration produces profound effects in an established MC38 tumor model, leading to the regression of tumors in a dose-dependent manner.

For more information on Kymab please see http://www.kymab.com.

Forward-looking statements

This announcement includes forward-looking statements that involve risks, uncertainties and other factors, many of which are outside of our control, that could cause actual results to differ materially from the results discussed in the forward-looking statements. Forward-looking statements include statements concerning our plans, objectives, goals, future events, performance and/or other information that is not historical information. All such forward-looking statements are expressly qualified by these cautionary statements and any other cautionary statements which may accompany the forward-looking statements. We undertake no obligation to publicly update or revise forward-looking statements to reflect subsequent events or circumstances after the date made, except as required by law.

Contacts:

Media US Dan Budwick, 1AB [e-mail] (mailto:[e-mail])

Media UK Consilium Strategic Communications Mary-Jane Elliott / Sukaina Virji / Melissa Gardiner [e-mail] (mailto:[e-mail]) Tel: [phone]

Investors Brandon Lewis [phone] [e-mail] (mailto:[e-mail])