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People with IgAN, an autoimmune disease which causes inflammation and fibrosis in the kidneys, are typically diagnosed in their 20s and 30s. Half eventually experience kidney failure.Handout

Shares in Chinook Therapeutics Inc. rose for a second straight day Friday after the Canadian-American drug developer reported promising preliminary results for two drugs it is developing to treat a rare kidney disease.

Chinook said early Thursday that eight subjects taking its BION-1301 antibody for IgA nephropathy (IgAN) had experienced a 48.8 per cent reduction in protein in their urine, or proteinuria – a key measure of the drug’s success – after six months. Then on Friday, Chinook revealed that 11 subjects taking its atrasentan drug for IgAN had experienced a 58.5 per cent reduction in proteinuria after 24 weeks; all but one had a reduction of 40 per cent or more.

Both data points “vastly exceeded our expectations,” Chinook CEO Eric Dobmeier said in an interview. “This is some of the best IgAN data ever reported and a game changer for this disease.”

Chinook’s Nasdaq-traded stock rose 10 per cent on Thursday on the BION-1301 news and 8.4 per cent Friday after publication of the atrasentan data. It closed the week at US$15.01.

Bloom Burton analyst Antonia Borovina noted the data on the two drugs was from a small number of IgAN patients with no placebo control group for comparison. But she added in a research report both results were well above levels considered to be “clinically meaningful,” adding: “We believe Chinook has two blockbuster drugs that have been significantly de-risked.” She increased her stock price target to US$48 per share from US$40 and said given Chinook’s “steady stream of positive data” and quality of drugs in development, that its stock “continues to be significantly undervalued.”

People with IgAN, an autoimmune disease which causes inflammation and fibrosis in the kidneys, are typically diagnosed in their 20s and 30s. Half eventually experience kidney failure. There are an estimated 500,000-plus people with the disease between the U.S., Europe and Japan, and millions more throughout Asia. There is only one recently approved therapy for IgAN, a steroid called Tarpeyo; people are typically treated with a combination of blood pressure-lowering medications, steroids and other unapproved drugs.

Chinook is running a separate, advanced efficacy human trial for atrasentan involving 320 patients, with half of participants set to receive the drug and the balance taking a placebo. Results are expected in 2024. Mr. Dobmeier said this week’s results were from “more of a signal-seeking trial” adding that despite the lack of a control group, “it really does provide strong evidence that this drug is working well in IgAN patients.”

While it’s unclear yet how the drugs would perform longer-term, Mr. Dobmeier said six months of clinically superior results to existing treatments from expanded human trials should help win accelerated approval from the U.S. Food and Drug Administration to get atrasentan to market.

Chinook was created in Vancouver in 2019 by venture capital firm Versant Ventures (its 160 employees are split between B.C., Seattle and Oakland). That year it licensed atrasentan from AbbVie Inc., which had abandoned efforts to develop it for diabetic kidney disease. But the drug giant had also tested it on 5,000 humans, meaning there was substantial safety data for Chinook to work with (the main side effect is fluid retention). That enabled it to put atrasentan directly into human efficacy trials, foregoing animal and human safety trials that typically take years.

The company picked up BION-1301 in 2020 when it merged with publicly traded Aduro Biotech Inc., which had tried and failed to develop it for cancer treatments.

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