Sangamo Therapeutics stock falls 23% on results of cutting-edge gene editing trial

Shares of Sangamo Therapeutics Inc. fell 23% in very active trading on Wednesday morning after the company released the first results of a gene-editing trial for a rare metabolic disorder called Hunter's Syndrome.

The trial marked the first instance of gene editing, or the addition of a new copy of a gene in the DNA of a patient's cells, completed inside the body, or in vivo, in the sangamo.

SGMO, -21.39%

I said. In the United States, in other types of gene editing and gene therapy that have been tested or approved, the process ends outside the body.

Two patients in the Sangamo trial presented reductions in a key biomarker called urinary glycosaminoglycans (GAG) after 16 weeks of treatment. Because of the enzyme deficiency of people with Hunter's syndrome, GAGs tend to accumulate in the body.

But the company said that she was not able to measure changes in the missing enzyme, called iduronate-2-sulfatase (IDS), 16 weeks after treatment because her activity in plasma "was below the level of quantification of the current test. "

Sangamo sought to play the changes in the GAGs observed in the trial and described the results as encouraging. But the company also admitted that it could not yet say whether the gene's candidate, the SB-913, could replace the enzyme replacement therapy currently used to manage the symptoms of Hunter's syndrome.

"We want GAGs to be reduced and reduced when the patient withdraws his enzyme replacement therapy," said a company executive on Wednesday. "I think if the patient had to take our medication and enzymatic replacement, it's a less attractive proposition."

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Hunter syndrome, also known as MPS II, mainly affects boys and causes progressive cell damage. A very rare disease, it affects about 500 patients in the United States, according to Sangamo.

The Sangamo gene editing technique, which is named after zinc finger proteins that bind to DNA, aims to treat Hunter's syndrome by adding a new copy of a gene in the DNA of cells. hepatic of a patient. The goal is to produce "a continuous and stable supply of the missing human enzyme IDS," said the company.

The Phase 1/2 trial, called "Champions", included six patients in total, divided into three groups ranging from low to medium doses and high SB-913. SB-913 was generally well tolerated, according to Sangamo; Although two serious side effects were observed, the investigator decided that they were primarily related to the disease and not to the treatment.

Sangamo highlighted the results for two patients at the average dose of treatment. Registration and dosing of patients in the high-dose cohort have been completed, the company said, with expected results in the coming months.

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The company also suggested that the results for the GAGs could be sufficient, describing the measure as what brought Elaprase, the

SHPG, -1.13%

enzymatic replacement therapy for Hunter syndrome, approved.

Elaprase targets GAG, and decreases in urinary GAG levels were observed after treatment, but the main result of therapy in the trials was that it improved walking ability in patients, according to its prescribing information. .

Sangamo also said on Wednesday that he has also developed new versions of the gene editing technique that could be many times more efficient, so "even if the third generation is not efficient, there are other possibilities" said a manager on Wednesday. call.

The company also develops programs for hemophilia A and B, MPS I, beta-thalassemia and more.

Corporate stocks fell 11% in the last three months, compared with a 5% increase in the S & P 500.

SPX, -0.39%

and a 4.6% rise in the Dow Jones Industrial Average Index

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.