Muscle disorder biotech Avidity aims for the clinic with $100M IPO

Six months after banking a $100 million venture round, Avidity Biosciences is heading to the public market. The company filed to raise up to $100 million in its IPO, which will push its lead muscle disorder program through IND-enabling studies and into the clinic in 2021.

The company aims to take antibody-drug conjugates (ADCs) to the next level by combining antibodies with oligonucleotides—or short DNA or RNA molecules. Attaching drugs to antibodies to take advantage of their selective nature isn’t a new idea. Multiple players are working on ADCs to deliver cell-killing drugs to cancer cells without affecting healthy tissue, but fewer than 10 ADCs have been approved because of the complexity of this class of drugs.

Avidity believes using oligonucleotides could work even better than cytotoxic drugs.

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"[The] payload is designed to be highly specific to a disease-related RNA rather than a highly toxic small molecule designed to kill the targeted cell," said Kent Hawryluk, Avidity's chief business officer, in an email last year.

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Avidity is developing its lead antibody-oligonucleotide conjugate (AOC), AOC 1001, for a form of myotonic dystrophy, a muscle wasting disorder caused by a mutation in the DMPK gene. People with Type 1 myotonic dystrophy produce abnormal DMPK RNA, which prevents cells in their muscles and other tissues from working properly.

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AOC 1001 comprises a monoclonal antibody that binds to TfR1, a transporter protein, and a small interfering RNA designed to lower patients’ levels of DMPK RNA. Avidity plans to start a phase 1/2 study of the treatment by the end of 2021, according to a securities filing.

The IPO haul will also bankroll a pair of earlier-stage AOCs for muscle atrophy and Duchenne muscular dystrophy, Avidity said in the securities filing. Its Duchenne efforts will focus on patients with certain types of mutations—those whose disease is amenable to skipping exons 44, 45 or 51. The FDA approved Sarepta Therapeutics’ Exondys 51 in 2016 for those whose disease is amenable to exon 51 skipping—about 13% of Duchenne patients.