Avrobio Inc (NASDAQ:AVRO) announced follow-up data demonstrating a durable treatment effect across key measures out to 36 months from a Phase 1/2 trial of an investigational gene therapy for cystinosis, dubbed AVR-RD-04.

Cystinosis is characterized by the accumulation of the amino acid cystine (a building block of proteins) within cells due to deficient protein cystinosin.

Excess cystine damages cells and often forms crystals that can build up and cause problems in many organs and tissues.

The patient's hematopoietic stem cells (HSCs) were genetically modified to express a functional version of cystinosin.

Preliminary data suggest that post-gene therapy produces functional cystinosin throughout the body, and neurocognitive tests suggestive of activity in the central nervous system. 

No adverse events (AEs) related to the drug product or serious adverse events have been reported.

Leukocyte cystine levels in the blood have decreased below baseline in all six patients and stabilized up to 36 months out from treatment. 

Skin and gastrointestinal mucosa biopsies reveal a decline in tissue cystine crystals below baseline in the first four patients, who have been observed for at least 12 months, with two patients observed up to 24 months.

Preliminary data from this trial suggest that this HSC gene therapy is well tolerated, with no AEs related to the drug product to date. 

The company plans to initiate late-stage cystinosis trial activities in 2H 2023, subject to regulatory alignment.

Price Action: AVRO shares are up 34% at $0.77 on the last check Thursday.