The charity auction Only Watch has raised nearly 100 million euros over the past 18 years, and watch executives have credited it with uniting fiercely competitive brands around a charitable cause, fostering collaborations and sparking creativity.

But just days before its scheduled Nov. 5 auction in Geneva, the fund-raiser canceled its 10th edition in response to numerous demands on social media for financial transparency.

“The time necessary to address questions and remarks in depth and consolidate trust — also by implementing changes — did not coincide with the short time left before the auction,” Luc Pettavino, a founder of the Association Monégasque contre les Myopathies (in English, Monegasque Association Against Myopathies), wrote in an email in response to questions from The Times. “Therefore, we took the decision to postpone the auction to 2024.” A new date has not been announced.

The association is a Monaco-based charitable foundation created in 2001 after Mr. Pettavino’s son, Paul, was diagnosed with Duchenne muscular dystrophy, one variation of the degenerative muscular disease. Only Watch, established in 2005 under the patronage of Prince Albert II of Monaco to support the foundation, has auctioned one-of-a-kind timepieces donated by their makers and sold without commissions or reserve prices.

From disappointing early editions, Only Watch grew to become one of the most high-profile events in the watch world — where notable records were set, like the $33.6 million paid for a Patek Philippe Grandmaster Chime in 2019.

While questions about the foundation’s funds had been raised in the past, the recent action followed an Instagram story posted on Oct. 4 by Ali Maghami, a prominent watch collector known online as Santa Laura. (His Instagram account is private but has 23,700 followers, including many well-known figures in the watch world.)

“I was seeing a lot of Champagne sipping at Only Watch events, but nothing about medical research,” Mr. Maghami said in a phone interview from Singapore, where he is based. “I had placed bids in Only Watch in the past, and as a participant in the auction, I want to know where the money is going, and if it is being spent to support the cause.”

In a series of posts and stories over a few days, Mr. Maghami demanded information about the charity’s governance and audited financial records under the headline “The community demands answers.” Hundreds of comments followed, as did news stories in some Swiss media and watch publications such as Revolution and Business Montres & Joaillerie. Many echoed the call for financial transparency.

On Oct. 8, Mr. Pettavino, as chairman of the association, issued a “Letter to the Watch Community,” along with a list of financial disbursements that showed almost half of the approximately $106 million it raised, had mainly gone to two biotech companies: SQY Therapeutics, based in France, and Synthena, in Switzerland. Mr. Pettavino is a founder of both businesses.

The remaining funds were in the association’s bank accounts, the letter said, “rigorously managed to ensure that we are ready for the next steps.”

The letter also noted that, until mid-September, Monegasque law required only that the association make its financial records available to the state and its administration. But a new ordinance, dated Sep. 14, now requires Monegasque associations with annual budgets exceeding €500,000 to file audited financial statements with the state.

“We will share our certified financial statements in the first trimester 2024,” Mr. Pettavino wrote to The Times.

As for the medical research that the association has funded, Mr. Pettavino wrote that one drug has been in human clinical trials since June. “Let me emphasize how complex, rare and outstanding it is for a small charity to put together the means and the team of researchers who in a limited time developed a proprietary molecule validated by the French/European sanitary authorities” to go to clinical trials, he wrote.

But, Mr. Maghami said, “Only Watch must explain the quality of the research it has funded since 2005. Other researchers are so far ahead, they have already developed F.D.A.-approved drugs for Duchenne. Wouldn’t it make more sense to use the money to support those researchers?”

Several drugs are available for Duchenne patients, and as recently as Oct. 26 the U.S. Food and Drug Administration approved Agamree, developed by Santhera Pharmaceuticals of Pratteln, Switzerland, with support from the Muscular Dystrophy Association, for the treatment of children and adolescents.

“I have raised these issues with Only Watch since 2017,” Gregory Pons of Business Montres & Joaillerie said in a phone interview. “Many brands did as well, but we never received satisfactory responses.”

Mr. Pettavino, however, wrote to The Times that “the community was regularly updated on progress of research through letters, videos or in-person meetings with researchers.”

Only Watch had announced that the Nov. 5 auction, which was to be conducted by Christie’s, would feature more than 60 timepieces donated by companies including Bulgari, F.P. Journe, Audemars Piguet and Tudor. In early September, some of the watches were displayed in several cities around the world to promote the sale.

Audemars Piguet canceled its participation in mid-October, pulling the Royal Oak Flying Tourbillon it had donated. The brand declined to make any comment.

But throughout the controversy, many well-known watchmakers have voiced their support for Mr. Pettavino: In an open letter on Instagram, the watchmaker François-Paul Journe expressed his “total confidence”; and the watchmaker Konstantin Chaykin released a statement via email praising him for inspiring brands “to create unique pieces which would not exist without this initiative.”

“This auction,” Maximilian Büsser, founder of MB&F, said in a recent interview, “was the only time the watch community would come together for a good cause. This is a sad situation, because what Only Watch has achieved is extraordinary.”

The H. Moser x MB&F Streamliner Pandamonium, a collaboration between the two brands, had been one of the 2023 auction donations. Would Mr. Büsser contribute again if Only Watch returns?

“Absolutely,” he said.