to Develop and Accelerate Next-Generation RNA-based Gene-Editing Technology, RetroT™

— Myeloid’s novel RetroT™ technology may enable targeted insertion of gene-sized DNA sequences into the genome, creating new opportunities for programmable gene editing

— Myeloid received a $45 million upfront payment from Prime, and is eligible for significant future milestone payments —

CAMBRIDGE, Mass, March 31, 2022 – Myeloid Therapeutics, Inc. (“Myeloid”), a clinical stage mRNA-immunotherapy company developing novel therapies for cancer and autoimmune diseases, today announced that it has entered into an exclusive option and research collaboration agreement with Prime Medicine, Inc. (“Prime”), a company founded to deliver on the promise of Prime Editing. The partnership focuses on accelerating the development of Myeloid’s proprietary RNA-based, retrotransposon mediated gene-insertion technology, (RetroT™), which has applications in gene editing and delivery and may be complementary to Prime Editing.

“At Myeloid, we are pleased to have built one of the deepest RNA-based technology platforms focused on multiple therapeutic modalities, including our newest technology announced today for gene editing, RetroT™,” said Daniel Getts, MBA, Ph.D., CEO of Myeloid. “This partnership highlights the broad applicability of our R&D engine to indications beyond cancer. We are excited to be working with Prime, a preeminent gene editing company, to continue pushing the boundaries of what mRNA can do, including gene delivery.”

Myeloid’s RetroT™ delivers genetic sequences and integration enzymes in a single mRNA strand. This breakthrough technology offers the potential to deliver gene-sized pieces of DNA into the genome, which are larger than currently possible with existing gene editing technologies. RetroT™ holds the potential to significantly expand the type and scope of genetic errors that can be reversed in situ.

Myeloid and Prime will collaborate to optimize Myeloid’s RetroT™ technology, with the goals of extending its utility to multiple cell types, increasing its efficiency and expanding its programmability so that it can be directed to pre-specified target sites within the genome. If successful, this technology could be used alongside Prime Editing to transform and vastly simplify the delivery of both ex vivo and in vivo cell therapies for the treatment of human diseases.

“We are committed to expanding our gene editing toolbox with new, uniquely positioned approaches that may complement Prime Editing,” said Keith Gottesdiener, M.D., CEO of Prime Medicine. “We look forward to partnering with the extremely talented team at Myeloid – including many experts in retrotransposon biology – to advance this novel technology, with the goal of expanding the applicability of Prime Editing to more broadly address human diseases. ”

Under the terms of the agreement, Myeloid received an upfront payment of $45 million. Myeloid is also eligible to receive significant milestone and option exercise payments and sales-based royalties. The companies will work together to address key elements required for translating Myeloid’s RetroT™ technology into human clinical products. Upon completion of these efforts, Prime will have the exclusive option to gain control of the intellectual property estate to expand upon its existing technology platform.

About Myeloid’s RetroT™ Technology Platform
Retrotransposons are genetic elements that replicate through reverse transcription of an RNA transposition intermediate. They contribute to structural changes and more importantly to gene regulation. Myeloid’s RetroT™ technology relies on mRNA to deliver genetic sequences and integration enzymes in a single mRNA strand. This breakthrough technology offers the potential to deliver gene-sized pieces of DNA into the genome, which are larger than currently possible with existing gene editing technologies. As a result, it holds the potential to significantly expand the type and scope of genetic errors that can be reversed in situ.

About Myeloid Therapeutics
Myeloid Therapeutics is a clinical stage mRNA-immunotherapy company developing novel therapies for cancer and autoimmune diseases. Integrating the fields of RNA, immunology and medicine, the Company’s proprietary platform provides clinical solutions by matching therapeutic modalities to disease conditions, including use of autologous cell therapies, in vivo cell programming using mRNA, RNA-based gene-editing using RetroT™ and multi-targeted biologics.

About Prime Medicine
Prime Medicine, Inc. is a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, Prime Editors, to address the widest spectrum of diseases by deploying Prime Editing technology. For more information, visit www.primemedicine.com or LinkedIn.

Myeloid Investor Contact
Amy Conrad
Juniper Point
[email protected]
858-914-1962

Myeloid Media Contact
Ryo Imai
Finsbury Glover Hering (FGH)
[email protected]
949-293-2928

Prime Medicine Media Contact
Dan Budwick
1AB
[email protected]