Rocket Pharmaceuticals Announces Publication of Manuscript Evaluating Mosaicism in Fanconi Anemia

Rocket Pharmaceuticals, Inc. (NASDAQ: RCKT) ("Rocket"), a clinical-stage company advancing an integrated and sustainable pipeline of genetic therapies for rare childhood disorders, announces the recent publication of a peer-reviewed manuscript: the first comprehensive review of somatic mosaicism in Fanconi Anemia (FA) in the journal Annals of Hematology. The review, entitled, "Mosaicism in Fanconi Anemia: Concise review and evaluation of published cases with focus on clinical course of blood count normalization," summarizes the existing literature regarding mosaicism in FA, a phenomenon previously described as "natural gene therapy." Mosaicism occurs when a spontaneous second mutation occurs in an (already-mutated) FA gene, resulting in a functional FA protein and restored cellular DNA-repair capacity. When this type of reversion or compensatory mutation occurs in hematopoietic stem cells (HSCs), these cells have at times been capable of restoring a more normalized blood and bone marrow environment, in some cases over multiple decades. The review provides the FA community with an additional resource to better understand the phenomenon and further supports Rocket's approach of treating patients with RP-L102, the Company's gene therapy candidate for FA, without a pre-treatment conditioning regimen.

"Although mosaicism in FA has been discussed within the physician and research community for more than two decades, uncertainty about the clinical significance of reversion mutations has remained," said Jonathan Schwartz, M.D., Chief Medical Officer and Senior Vice President of Rocket. "Importantly, findings from this review support the selective growth advantage for gene corrected stem cells over diseased stem cells which potentially obviates the need for conditioning in FA gene therapy. In addition to allowing us to better understand how RP-L102 may best help patients, we hope that bringing these data together into a cohesive review can better help the entire FA community as we work together to optimize treatment options."

The publication includes a literature-based assessment of FA mosaicism and identification of a cohort of cases that most likely emanated from reversion in long-term repopulating HSC populations. Additionally, the manuscript details diagnostic methods and outcomes of published cases of mosaicism with an evaluation of cases in which FA mosaic patients were followed long-term in a clinical setting. These findings provide additional detail on the mechanism and chronology by which gene corrected cells may repopulate patients' blood and bone marrow following treatment with Rocket's gene therapy candidate, RP-L102, which is currently being investigated in a global Phase 2 registration-enabling study.

"We are grateful for the opportunity to bring together several decades of diligent reports from investigators in many parts of the world, including our collaborators in Spain and the United States," added Dr. Schwartz, "and we look forward to facilitating additional global bench-to-bedside collaborations as the Phase 2 clinical program progresses."

The Phase 2 trial (NCT04069533, NCT04248439) is designed to assess the therapeutic efficacy of RP-L102 in patients with FA. Patients are treated with RP-L102 "Process B" which incorporates a modified stem cell enrichment process, transduction enhancers, as well as commercial-grade vector and final drug product. Improved mitomycin-C (MMC) resistance in bone marrow colony forming (progenitor) cells is the primary endpoint and may also serve as a surrogate endpoint for accelerated approval.

About Fanconi Anemia

Fanconi Anemia (FA) is a rare pediatric disease characterized by bone marrow failure, malformations and cancer predisposition. The primary cause of death among patients with FA is bone marrow failure, which typically occurs during the first decade of life. Allogeneic hematopoietic stem cell transplantation (HSCT), when available, corrects the hematologic component of FA, but requires myeloablative conditioning. Graft-versus-host disease, a known complication of allogeneic HSCT, is associated with an increased risk of solid tumors, mainly squamous cell carcinomas of the head and neck region. Approximately 60-70% of patients with FA have a FANC-A gene mutation, which encodes for a protein essential for DNA repair. Mutation in the FANC-A gene leads to chromosomal breakage and increased sensitivity to oxidative and environmental stress. Chromosome fragility induced by DNA-alkylating agents such as mitomycin-C (MMC) or diepoxybutane (DEB) is the ?gold standard' test for FA diagnosis. Somatic mosaicism occurs when there is a spontaneous correction of the mutated gene that can lead to stabilization or correction of a FA patient's blood counts in the absence of any administered therapy. Somatic mosaicism, often referred to as ?nature's gene therapy' provides a strong rationale for the development of FA gene therapy because of the selective growth advantage of gene-corrected hematopoietic stem cells over FA cells¹.

¹Soulier, J.,et al. (2005) Detection of somatic mosaicism and classification of Fanconi anemia patients by analysis of the FA/BRCA pathway. Blood 105: 1329-1336

About Rocket Pharmaceuticals, Inc.

Rocket Pharmaceuticals, Inc. (NASDAQ: RCKT) ("Rocket") is advancing an integrated and sustainable pipeline of genetic therapies that correct the root cause of complex and rare childhood disorders. The company's platform-agnostic approach enables it to design the best therapy for each indication, creating potentially transformative options for patients contending with rare genetic diseases. Rocket's clinical programs using lentiviral vector (LVV)-based gene therapy are for the treatment of Fanconi Anemia (FA), a difficult to treat genetic disease that leads to bone marrow failure and potentially cancer, Leukocyte Adhesion Deficiency-I (LAD-I), a severe pediatric genetic disorder that causes recurrent and life-threatening infections which are frequently fatal, and Pyruvate Kinase Deficiency (PKD) a rare, monogenic red blood cell disorder resulting in increased red cell destruction and mild to life-threatening anemia. Rocket's first clinical program using adeno-associated virus (AAV)-based gene therapy is for Danon disease, a devastating, pediatric heart failure condition. Rocket's pre-clinical pipeline program is for Infantile Malignant Osteopetrosis (IMO), a bone marrow-derived disorder. For more information about Rocket, please visit www.rocketpharma.com.

Rocket Cautionary Statement Regarding Forward-Looking Statements

Various statements in this release concerning Rocket's future expectations, plans and prospects, including without limitation, Rocket's expectations regarding the safety, effectiveness and timing of product candidates that Rocket may develop, to treat Fanconi Anemia (FA), Leukocyte Adhesion Deficiency-I (LAD-I), Pyruvate Kinase Deficiency (PKD), Infantile Malignant Osteopetrosis (IMO) and Danon Disease, and the safety, effectiveness and timing of related pre-clinical studies and clinical trials, may constitute forward-looking statements for the purposes of the safe harbor provisions under the Private Securities Litigation Reform Act of 1995 and other federal securities laws and are subject to substantial risks, uncertainties and assumptions. You should not place reliance on these forward-looking statements, which often include words such as "believe," "expect," "anticipate," "intend," "plan," "will give," "estimate," "seek," "will," "may," "suggest" or similar terms, variations of such terms or the negative of those terms. Although Rocket believes that the expectations reflected in the forward-looking statements are reasonable, Rocket cannot guarantee such outcomes. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including, without limitation, Rocket's ability to successfully demonstrate the efficacy and safety of such products and pre-clinical studies and clinical trials, its gene therapy programs, the preclinical and clinical results for its product candidates, which may not support further development and marketing approval, the potential advantages of Rocket's product candidates, actions of regulatory agencies, which may affect the initiation, timing and progress of pre-clinical studies and clinical trials of its product candidates, Rocket's and its licensors' ability to obtain, maintain and protect its and their respective intellectual property, the timing, cost or other aspects of a potential commercial launch of Rocket's product candidates, Rocket's ability to manage operating expenses, Rocket's ability to obtain additional funding to support its business activities and establish and maintain strategic business alliances and new business initiatives, Rocket's dependence on third parties for development, manufacture, marketing, sales and distribution of product candidates, the outcome of litigation, and unexpected expenditures, as well as those risks more fully discussed in the section entitled "Risk Factors" in Rocket's Quarterly Report on Form 10-Q for the quarter ended September 30, 2019, filed November 8, 2019 with the SEC. Accordingly, you should not place undue reliance on these forward-looking statements. All such statements speak only as of the date made, and Rocket undertakes no obligation to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise.