Taysha Gene Therapies (TSHA) Acquires Exclusive Worldwide Rights to Clinical-Stage AAV9 Gene Therapy Program

April 12, 2021 7:16 AM EDT

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Taysha Gene Therapies, Inc. (Nasdaq: TSHA), a patient-centric, pivotal-stage gene therapy company focused on developing and commercializing AAV-based gene therapies for the treatment of monogenic diseases of the central nervous system (CNS) in both rare and large patient populations, today announced the acquisition of exclusive worldwide rights to a clinical-stage AAV9 gene therapy program, now known as TSHA-120, for the treatment of giant axonal neuropathy (GAN). TSHA-120 is an intrathecally dosed AAV9 gene therapy currently being evaluated in a clinical trial for the treatment of GAN. The trial is being conducted by the National Institutes of Health (NIH) in close collaboration with a leading patient advocacy group focused on finding treatments and cures for GAN. TSHA-120 has received rare pediatric disease and orphan drug designations from the U.S. Food and Drug Administration (FDA) for the treatment of GAN.

GAN is a rare inherited genetic disorder that affects both the central and peripheral nervous systems and is caused by loss-of-function mutations in the gene coding for gigaxonin. Many children with GAN show symptoms and features before the age of five, including progressive scoliosis, contractures, atrophy of the spinal cord, giant axons – also known as nerve fibers – and abnormalities of the white matter in the brain. Currently, there are no approved treatments for GAN, which often results in death for patients in their late teens or early twenties. TSHA-120 was originally developed in the laboratory of Taysha’s Chief Scientific Advisor, Dr. Steven Gray, and advanced in a historic ongoing clinical trial by the NIH as the first intrathecally dosed gene therapy study.

“Dr. Steven Gray’s work on the GAN program was the catalyst for all the other translational research initiatives in his lab and we are very pleased to continue this important and meaningful work that has had a significant impact across the entire gene therapy landscape. As the program that laid the foundation for our robust pipeline, we believe that TSHA-120 is a seamless strategic fit and will be immediately value-accretive for Taysha. TSHA-120 clinical data generated to date is a clear validation of our scientific approach with read-through to our existing product development pipeline. Consistent with all of our gene therapy candidates, TSHA-120 targets a monogenic CNS disease, is delivered intrathecally using a proven AAV9 vector, and utilizes a highly scalable HEK293 suspension manufacturing process. Collectively, these key parallels enable Taysha to leverage synergies across its core competencies to efficiently develop and commercialize TSHA-120,” said RA Session II, President, Founder and Chief Executive Officer of Taysha. “The efficacy data in preclinical studies with the GAN knockout rodent model were extremely compelling, and TSHA-120 demonstrated significant improvement in pathology across a range of tissues, and notably improved the pathological appearance of the dorsal root ganglia, which is a key component of disease progression. We look forward to quickly working with the regulatory agencies on a path forward to approval of TSHA-120, and in parallel, accelerating the build-out of our commercial infrastructure to support patient identification, payor engagement and product distribution. TSHA-120 has the potential to address a significant unmet need for an estimated 2,400 patients with GAN across the United States and in Europe, potentially representing a near-term commercial opportunity of greater than $2 billion.”

The National Institute of Neurological Disorders and Stroke (NINDS) division of the NIH is conducting the ongoing open-label, non-randomized, dose-escalation clinical trial of TSHA-120 for the treatment of GAN. The primary endpoint is safety, with secondary endpoints measuring efficacy using pathologic, physiologic, functional, and clinical markers. A primary measure of clinical efficacy is the Motor Function Measure 32 (MFM32) score, a quantitative scale designed to assess the severity and progression of motor function abilities. There is precedent for its use in multiple clinical studies for neuromuscular diseases, including spinal muscular atrophy amongst others. To date, 14 patients have been dosed with one of four dose levels of TSHA-120. TSHA-120 has demonstrated a dose-response relationship with arrest of disease progression at the second-highest dose level (1.8x1014 total vector genomes [vg]) at one-year post-treatment, affecting a statistically significant 8-point improvement on the MFM32 score. A 4-point change on the MFM32 score is considered clinically meaningful. Six of these patients treated at therapeutic dose levels have shown sustained dose-dependent improvements in MFM32 scores for more than three years. Long-term results demonstrated that treatment with TSHA-120 at multiple dose levels was well-tolerated with no severe drug-related adverse events. Additional data are expected later this year, including results from the highest dose cohort (3.5x1014 total vg).

“TSHA-120 is the first successful in-human intrathecal gene transfer in the history of gene therapy and, as such, has had a significant impact across the field. This program further supports our approach to treating monogenic diseases of the CNS and may enable us to pursue proof-of-concept for our redosing platform,” said Suyash Prasad, MBBS, M.SC., MRCP, MRCPCH, FFPM, Chief Medical Officer and Head of Research and Development of Taysha. “We are very encouraged by TSHA-120’s halting effect on disease progression at therapeutic dose levels and long-term durability of effect in patients living with GAN, and we look forward to highlighting the initial clinical data in an R&D Day in June 2021. In the meantime, we plan to engage regulatory agencies in the United States, Europe and Japan as soon as possible.”

Before the end of the year, Taysha intends to request an End-of-Phase meeting with the FDA and engage with the European Medicines Agency (EMA) and the Pharmaceuticals and Medical Devices Agency (PMDA) in Japan to discuss the regulatory pathway for TSHA-120. Taysha expects to provide a regulatory and clinical update on TSHA-120, including data from the 3.5x1014 total vg cohort by year-end.

Under the terms of the agreement, in exchange for granting Taysha the exclusive worldwide rights to TSHA-120, the leading GAN patient advocacy group will receive an upfront payment of $5.5 million and will be eligible to receive clinical, regulatory and commercial milestones totaling up to $19.3 million, as well as a low, single-digit royalty on net sales upon commercialization of the product.

Conference Call and Webcast Information

Taysha management will hold a conference call and webcast today at 8:00 am ET / 7:00 am CT to review its acquisition of the GAN program. The dial-in number for the conference call is 877-407-0792 (U.S./Canada) or 201-689-8263 (international). The conference ID for all callers is 13718632. The live webcast and replay may be accessed by visiting Taysha’s website at https://ir.tayshagtx.com/news-events/events-presentations. An archived version of the webcast will be available on the website for 60 days.

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