Suyash Prasad
Analyst · Goldman Sachs. Please proceed with your question
Thanks, RA. We have made significant progress in the second quarter and continue to achieve important clinical advancements that further support a potential regulatory approval of our most advanced program, TSHA-120, which holds significant promise for patients with giant athermal neuropathy, or GAN. At our R&D Day, in addition to the compelling clinical data demonstrating halting of disease progression as assessed by the well-validated and established motor assessment tool, the MFM32, we presented new visual acuity data from the ongoing Phase 1/2 trial investigating TSHA-120 in patients with GAN. In children and adolescents with GAN, there is an ongoing and progressive deterioration in vision towards blindness, which is understandably one of the most challenging and upsetting symptoms from the perspective of the patient and family. With this new data, we were able to demonstrate a dose-dependent trend towards stabilization of visual acuity, i.e., the ability of AAV9 gene therapy to preserve visual function, which otherwise would be lost. We also discussed in depth the natural history data in GAN that was published in the highly regarded neurology journal, Brain earlier this summer. As a reminder, all GAN natural history data was generated and supported by the National Institute of Neurological Disorders and Stroke, or NINDS under the leadership of the principal investigator, Carsten Bönneman. Included in the publication was the largest cohort of genetically confirmed patients with early and late onset forms of GAN. This large cross-sectional analysis highlighted clinical differences between patients with early onset versus late onset GAN based on performance on the MFM32, a validated and well-known scale to measure strength and motor function as well as other functional motor scales and disease markers. Additionally, a robust assessment of many clinically relevant outcome measures for GAN was performed, including motor, sensory, respiratory, neurophysiologic, MRI and biopsy assessments. Moreover, this was the first clinical study ever to formally and comprehensively evaluate autonomic nervous system dysfunction in a cohort of individuals with GAN. Overall, this natural history study has been instrumental in clinical trial design for the ongoing Phase 1/2 trial and the data included in the Brain publication will serve as baseline data for the natural history comparator arm to the interventional study. As already noted, we remain on track to report clinical data from the highest dose cohort from this ongoing Phase 1/2 trial in the second half of this year and to provide a regulatory update on the program by year end. We have also made significant progress across our preclinical programs. Positive preclinical data for TSHA-102 and Rett syndrome was published also in the Journal of Brain that provided quantitative evidence of MIRA’s ability to exhibit genotype dependent regulation of MECP2 gene expression on a cell-by-cell basis across different regions of the brain in both wild-type and knockout mouse models of Rett syndrome. We recently have productive and collaborative pre-IND CTA discussions with several key regulatory agencies and received positive feedback that support our anticipated IND/CTA submission in the second half of this year. In GM2 gangliosidosis, we were able to discuss in detail at our R&D Day had the existing and in-depth natural history data on this condition informs us about disease progression and in particular motor development delays. We believe these data help provide a comparator for ongoing and future interventional trials. We continue to expect preliminary safety and biomarker data in the Queens University Phase 1/2 trial for TSHA-101 in the second half of this year. Specifically, we will be disclosing HEXA enzyme activity in serum and CSF and expect that 5% HEXA enzyme activity will be considered a positive result. In the U.S., we had a productive and informative meeting with the FDA. We remain on track to initiate a Phase 1/2 trial in the second half of this year. Moving on to our CLN1 program, additional preclinical data for TSHA-118 were presented at R&D Day, which was demonstrated sustained preservation of motor function and rescue with higher doses of TSHA-118 and earlier intervention in CLN1 knockout mice. There are two ongoing natural history studies assessing CLN disease, which will help further our understanding of the disease, inform on our clinical trial design and serve as comparative data in a future trial for TSHA-118. These two studies include a prospective observational study assessing the natural history of CLN diseases and the retrospective and the prospective study to characterize the age-at-onset of major symptoms and the relationship between age and severity. TSHA-118 currently has an open IND. We recently have very productive and collaborative meetings with several key regulatory agencies and positive feedback that support dosing of the first patient, which we anticipate should occur in the second half of this year. TSHA-118 has been granted orphan drug designation, rare pediatric disease designation and fast track designation from the FDA and orphan medicinal product designation from the EMA for the treatment of CLN1 disease. For TSHA-104 in SURF1-associated Leigh syndrome, we announced at R&D Day, new data demonstrating that only a small increase in COX-1 activity can significantly improve the clinical phenotype in these patients, further supporting our SURF1 gene replacement strategy with TSHA-104. Reduced tox activity also correlated with disease worsening in patient fibroblasts, further supporting the impact of COX activity on disease outcomes. This phenomenon draws correlations to other diseases that we are targeting, including GM2 and CLN1, while small increases in activity can have a pronounced physiological impact. We plan to file an IND/CTA for TSHA-104 in the second half of this year. Additionally, a natural history study that is part of our clinical development program is expected to enroll its first patient. This study will follow patients for initial period of time prior to enrollment into the interventional trial. At our R&D Day, Dr. Rachel Bailey, Assistant Professor in the Department of Pediatrics at UT Southwestern, presented positive preclinical data for TSHA-105 in SRC39 deficiency that demonstrated improvement of EEG activity and reduction in seizures and associated deaths in SLC13A5 knockout mice. We continue to advance TSHA-105 towards the clinic and expect that patients currently enroll in an ongoing prospective natural history study would be available to enter our clinical trial. We are currently considering an open label randomized dose escalation Phase 1/2 trial to examine the safety, tolerability and preliminary efficacy of TSHA-105 in the treatment of SLC13A5 deficiency. Biomarkers include citrate levels in the plasma, urine and CSF. Moving on to TSHA-103 in SLC6A1 haploinsufficiency disorder at our R&D Day, Dr. Kim Goodspeed, Assistant Professor in the Department of Pediatrics, Neurology and Psychiatry at UT Southwestern and Dr. Steven Gray, Associate Professor in the Department of Pediatrics at UT Southwestern and Chief Scientific Advisor at Taysha, highlighted the nature of the disease and the positive preclinical data to-date. In SLC6A1 knockout and heterozygous mouse models, CNS administration of TSHA-103 rescued abnormal seizure activity, notably recently obtained positive data demonstrating rescue or functional measures such as nesting, open field activity, hind limb clasping and latency to fall from the rotarod. We are now evaluating dose and age response and finalizing the dose from our preclinical pharmacology experiments. We are also developing an interventional trial protocol. In APBD and Lafora, Dr. Berge Minassian, Division Chief of Pediatric Neurology at UT Southwestern and Chief Medical Advisor at Taysha provided an in-depth discussion about the nature of both diseases at our R&D Day and highlighted positive preclinical data that supports advancement of these programs. Specifically, TSHA-112 reduced GYS1 expression in the APBD knockout model, which resulted in decreased polyglucosan body formation in mice brain. TSHA-111-LAFORIN and TSHA-111-MALIN reduced GYS1 expression in the LAFORIN and MALIN knockout models, which resulted in decreased Lafora body formation in mice brain. We continue to make good progress on both programs and are currently developing an interventional trial protocol. Preclinical data for TSHA-113 in tauopathies presented at R&D Day demonstrated significant reduction in tau mRNA and protein levels, validating the potential use of AAV-mediated gene silencing to achieve lifelong reduction of tau protein levels and supporting further preclinical development for the treatment of tauopathies. Lastly, we were very excited to highlight at our R&D Day on novel approaches to treat Angelman syndrome. We are targeting the entire Angelman syndrome population via knockdown of UBE3A-ATS to unsilenced the paternal allele and also using a gene replacement strategy on UBE3A to mimic the maternal UBE3A allele expression. We have shown compelling fluorescence images of the cerebellum that demonstrates UBE3A expression following administration of TSHA-106, our short hairpin RNA candidates. As you can see, our robust portfolio of clinical and preclinical candidates continues to advance expeditiously. And as RA noted, we have a number of clinical and regulatory catalysts expected in the second half of the year. We will continue to provide updates on our programs throughout the year. With that, I will turn the call over to Kamran to review our financial results.