Avidity Biosciences found an eager buyer for its neuroscience pipeline when Novartis shelled out approximately $12 billion to acquire the RNA drug developer, in a deal completed late last month.
But when it came to Avidity’s preclinical precision cardiology programs, including collaborations with Bristol Myers Squibb (BMS) and Eli Lilly, Novartis wasn’t as interested. So, the programs, plus two other programs pursuing undisclosed targets, were spun out into a new company formed to develop drugs capable of delivering RNA directly to the heart to treat rare, life-threatening genetic cardiomyopathies.
The spinout, Atrium Therapeutics, is funded with approximately $270 million in cash and cash equivalents. Atrium has identified two lead candidates: ATR 1072, a treatment for protein kinase AMP-activated non-catalytic subunit Gamma 2 (PRKAG2) syndrome, and ATR 1086, a treatment for phospholamban (PLN) cardiomyopathy.
Atrium plans to submit its first investigational new drug (IND) filing for a Phase I first-in-human trial of ATR 1072 in the second half of this year, while planning to submit an IND for ATR 1086 in 2027.
ATR 1072 uses a siRNA that works through a sequence-specific gene silencing mechanism to reduce PRKAG2 mRNA, normalize AMP-activated protein kinase (AMPK) activity, and reduce pathogenic glycogen accumulation, with the aim of improved heart function. ATR 1086 is designed to selectively reduce PLN expression in cardiac muscle in order to relieve sarco/endoplasmic reticulum calcium-ATPase 2a (SERCA2a) inhibition and restore calcium cycling dynamics, with the intent of improving cardiac performance.
Both candidates apply the Antibody Oligonucleotide Conjugate (AOC
) technology developed by Avidity. AOCs are designed to combine the tissue selectivity of monoclonal antibodies (mAbs) and other targeted delivery ligands with the precision of oligonucleotides.
“Our vision as Atrium is to really pioneer RNA therapeutics for the heart, and profoundly improve the lives of people living with cardiac diseases,” Kathleen (Kath) Gallagher, Atrium’s CEO, told GEN. “There is such a big unmet medical need for patients there with genetic cardiomyopathies who today are really just receiving symptomatic treatment. It’s a big opportunity for Atrium, and it’s exciting to be able to utilize a platform and a technology that we know so well to actually go into this space.”
Two-million-person market
Atrium has quantified that opportunity as a potential market that includes about two million people diagnosed in the United States with genetic cardiomyopathies, of which half have an underlying genetic driver of disease. With no therapies for such conditions yet approved, treatment consists largely of symptom management.
The two undisclosed candidates are both in research stages and designed to treat rare cardiomyopathies. “I wouldn’t expect to see anything on them in 2026,” Gallagher cautioned. “We’ve got our hands full in 2026.”
Atrium’s pipeline also includes collaborations with BMS and Eli Lilly that were launched by Avidity.
BMS committed $100 million upfront ($60 million cash and a $40 million purchase of Avidity stock). Avidity initially partnered with MyoKardia, which BMS acquired in 2020. In 2023, BMS and Avidity announced an expanded, up to $2.3 billion partnership, a global licensing and research collaboration focused on discovering, developing, and commercializing “multiple” cardiovascular targets. (Atrium disclosed “up to five,” in a January 29 regulatory filing.)
“We’re working actively with BMS on those as well. That collaboration is going quite well, and all of those programs are also in the precision cardio space,” Gallagher said.
In 2019, Lilly inked a global licensing and research collaboration with Avidity focused on developing treatments in immunology and other indications. Lilly agreed to pay Avidity $20 million cash upfront, invest $15 million in Avidity, and commit up to approximately $405 million per target in payments tied to achieving development, regulatory, and commercialization milestones, plus tiered royalties ranging from the mid-single to low-double digits on product sales.
Lilly paid Avidity a $10 million milestone payment in August for initiating a Phase I trial of one co-developed candidate. “Their first program has moved into the clinic, and there was a milestone payment for that last year. So, that collaboration is ongoing, but Lilly is really handling all of the work for that,” Gallagher said.
Applying lessons learned
Just as Avidity sought to deliver neuroscience RNA therapeutics outside of the liver, Atrium aims to apply what Avidity learned about the AOC platform to deliver RNA-based treatments for cardiovascular disorders. Gallagher said she does not foresee that quest being hindered by the sort of regulatory resistance experienced by developers of mRNA-based vaccines: “There are a lot of companies working in the RNA space, and I only see that growing.”
Atrium is one of several companies pursuing RNA therapies to treat various heart diseases.
In September, no less a figure than RNA interference (RNAi) drug pioneer John Maraganore, PhD, joined Clive Meanwell, MBChB, MD, founder and former CEO of The Medicines Co. and now co-founder and executive chair of Population Health Partners, to establish Corsera Health. Corsera has launched a Phase I trial of lead pipeline candidate COR-1004, a once-annual subcutaneous injection designed to reduce levels of PCSK9 and AGT, and completed an oversubscribed $80 million Series A financing in January.
Another company, Kardigan, has within its pipeline tonlamarsen, an antisense oligonucleotide designed to treat acute severe hypertension (ASH) by targeting and degrading angiotensinogen (AGT) mRNA in the liver. Discovered by Ionis Therapeutics, tonlamarsen is now licensed by Kardigan through an exclusive, worldwide development and commercialization agreement whose specifics have not been disclosed. Privately held Kardigan has raised more than $550 million—$300 million in Series A financing announced in January 2025, and a $254 million Series B round in October.
Atrium continues to trade on NASDAQ under the ticker symbol “RNA,” previously used by Avidity, now an indirect, wholly owned subsidiary of Novartis. From a closing price of $14.75 on the stock’s first trading day of February 27, Atrium shares have risen 14% to $16.77 on March 5 before tumbling 12.5% to $14.67 at Tuesday’s close of trading.
“Deep experience”
Gallagher joined Avidity in 2021 and served as its chief program officer from 2024 until taking the helm of Atrium, whose former CEO, Sarah Boyce, has joined the spinout as board chair.
“The team that we have at Atrium is a phenomenal group of people. We’ve all worked together for years. We have deep experience in the RNA field, as well as in rare diseases,” Gallagher said, explaining why she agreed to lead the spinout. “When I think about people, it’s also about patients, and there is a huge unmet medical need. The path-paving work we got to do at Avidity in the neuromuscular field is some of the most rewarding I’ve done in my career.
“Having the ability to do that again in genetic cardiomyopathy, it was just such an amazing opportunity to do that with people, and an amazing technology, and frankly with a strong balance sheet, where we can really make a difference for patients,” she added. “It is an incredible opportunity and privilege to get to be at the helm of Atrium.”
How did Atrium get its name? Gallagher said she and colleagues turned to ChatGPT for help, asking the artificial intelligence chatbot: “Hey, what are some cool names?”
“What we wanted was a name that was an actual word that you can look up in the dictionary,” Gallagher recalled.
In the end, it wasn’t AI but Steve Hughes, MD, the spinout’s chief medical officer, who came up with the name Atrium.
“It signifies the atrium in the heart. But also, it’s the fact that the atrium is the gathering place in most buildings, from an architectural reference,” Gallagher added. “We are very excited to have Atrium be a very welcoming and warm place for patients and for physicians, and we look forward to having them work with us and gather and have fun as we go through this process.”
Based in San Diego, Atrium has a workforce of about 50 people, with plans to grow by 10–15 people this year.
“I would say mostly development will probably be the area we’d be growing the most, and probably in manufacturing. Those are probably the two areas that we’ve got to do some building,” Gallagher said. “We look forward to growing and hiring where it makes sense, in the San Diego area and hybrid as well.”
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