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Trial dents confidence in Sangamo’s gene-editing tech

Company proposing switch to next-gen version

Sangamo

Shares in US biotech Sangamo have slumped after the company revealed a trial of a drug based on its gene-editing technology failed to hit the mark.

Sangamo said that interim results from the phase 1/2 CHAMPIONS study showed that a single injection of SB-913 for the rare genetic disease mucopolysaccharidosis type II (MPS II) or Hunter syndrome was able to induce expression of the IDS enzyme that is deficient in the disease.

The problem? Sangamo’s zinc finger nuclease (ZFN) drug wasn’t able to show an impact on biomarkers used to gauge the efficacy of MPS II drugs, and the company is now suggesting that it will have to switch its attention to a second generation of the ZFN design that it hopes will be more potent.

sandy

Sangamo's CEO Sandy Macrae

Sangamo CEO Sandy Macrae attempted to convince investors that the results were a step on the path to an in vivo gene-editing therapy that is “the most difficult, cutting-edge application of our technology”, but the stock still lost almost a third of its value before the markets closed yesterday, implying investors had expected an efficacy signal.

It’s not the first time that investors have been underwhelmed by data for Sangamo’s lead gene-editing drug, which is spearheading the use of ZFN technology as an alternative to other methods such as CRISPR and TALEN for in vivo gene editing.

Last September, preliminary data from CHAMPIONS suggested that SB-913 was able to reduce total levels of glycosaminoglycans (GAGs) that accumulate in MPS II and cause the widespread tissue and organ damage that eventually shortens patients’ lives. At that timepoint however it wasn’t able to show an increase in IDS expression.

The updated results included liver biopsy data which showed that an increase in IDS was seen in two of six patients in the study, providing molecular evidence that the gene-editing was working, but that was outweighed by the finding that there was no “meaningful change” in urinary GAG, the main marker for clinical efficacy.

Sangamo is still awaiting IDS expression and GAG data from the higher-dose cohort in the trial but Macrae said on a conference call that he has “a realistic view on whether this first generation of ZFNs will accomplish everything that patents need, particularly in the low- and mid-dose cohorts.”

Patients in the study are still being treated with Shire’s Elaprase (idursulfase), a recombinant form of IDS used as enzyme replacement therapy (ERT) in MPS II, and Macrae said: “we will need to wait and see how the high-dose cohort fares when ERT is withdrawn before anyone should interpret the meaning of the increased enzyme activity levels that we have observed.”

Sangamo also reported preliminary results from the EMPOWERS trial of its SB-318 drug for mucopolysaccharidosis type I (MPS I) which also showed that a single injection of the drug was able to induce expression of the IDUA enzyme missing in the disease, which is also known as Hurler syndrome.

On the plus side for the company, the FDA has apparently told the company it can fold the second-generation ZFNs into its existing clinical trial approvals, which should reduce the lead time, but there’s no doubt the new results represent a delay to its programmes.

Companies developing other gene-editing technologies, such as CRISPR Therapeutics, Intellia Therapeutics and Editas Medicine, also saw their shares close down, suggesting a knee-jerk reaction in the sell-off.

Article by
Phil Taylor

7th February 2019

From: Research

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