Sangamo Therapeutics Inc. stock dropped 23.6% on 6th September 2018, after the company released early results from a gene-editing trial for a rare metabolic disorder called Hunter syndrome. Shares continued their fall on 7th September, dropping 4.6%.
Two patients in the Sangamo trial had reductions of a key biomarker called urinary glycosaminoglycans (GAGs) after 16 weeks of treatment. Because of the enzyme deficiency that individuals with Hunter syndrome have, GAGs tend to accumulate in the body. But the company said that it wasn’t able to measure changes in the missing enzyme, called iduronate-2-sulfatase (IDS), 16 weeks after treatment, because its activity in plasma was below the level of the current assay quantification.
Sangamo sought to play up the changes in GAGs seen in the trial, and described results as encouraging. But the company also admitted that it could not yet say whether the gene-editing candidate, SB-913, could replace the enzyme replacement therapy that is currently used to manage Hunter syndrome’s symptoms.
The company is also developing programs for hemophilia A and B, MPS I, beta thalassemia and more. Of those, its hemophilia B program uses the same approach, or zinc finger nuclease genome editing. The stock has dropped 16% over the last three months, compared with a 4% rise in the S&P 500 SPX, +0.19% and a 3.4% rise in the Dow Jones Industrial Average DJIA, -0.23%.