Taysha Gene Plans Protocol Amendment After Patient Death In Gene Therapy Trial

Taysha Gene Therapies Inc TSHA reported initial serum β-hexosaminidase A (Hex A) enzyme activity data for TSHA-101 in patients with Sandhoff and Tay-Sachs diseases, two forms of GM2 gangliosidosis. 

• According to Taysha, TSHA-101 is the first bicistronic vector in clinical development. TSHA-101 is designed to cause the expression of two genes, HEXA and HEXB, that encode for subunits of the Hex A enzyme. 
• Mutations in HEXA and HEXB are responsible for Tay-Sachs and Sandhoff, respectively. 
• Hex A enzyme activity in the Sandhoff patient climbed to 190% of normal after one month and kept rising to hit 288% of normal by the third month. 
• Natural history data show Sandhoff patients have activity levels of 5% of normal, at most, leading Taysha to calculate the month one and three figures represent 38-fold and 58-fold jumps in activity, respectively.
• Taysha observed a rise in the Hex A enzyme in the Tay-Sachs patient. After one month, enzyme activity was 25% of normal, a fivefold increase over the 5% level at which patients become symptomatic.
• Investigators saw no significant drug-related events. However, the Sandhoff patient died several months after receiving TSHA-101. 
• The patient showed signs of clinical improvement three months after being treated and returned home. 
• The unvaccinated patient contracted an upper respiratory infection at home, possibly COVID-19, was hospitalized and died. 
• The initial assessment of the investigator deemed the death unrelated to TSHA-101.
• Price Action: TSHA shares are down 9.54% at $6.92 during the market session on the last check Thursday.