The ResMed Inc (ASX: RMD) share price is under pressure on Tuesday.

At the time of writing, the sleep disorder treatment company's shares are down 5% to $36.90.

Why is the ResMed share price tumbling?

Investors appear to have been hitting the sell button today after reacting to positive trial results from a potential future competitor in the obstructive sleep apnoea (OSA) treatment space.

This morning, US-based biotech company Apnimed announced that its lead candidate, AD109, delivered positive results in its Phase 3 SynAIRgy clinical trial.

What is AD109?

According to its release, AD109 is a once-daily oral pill designed to treat OSA by targeting the neuromuscular root cause of the condition.

In contrast to devices like ResMed's CPAP (continuous positive airway pressure) machines, which mechanically keep the airway open during sleep, AD109 aims to stimulate upper airway muscles pharmacologically. This offers what Apnimed calls a "simple, safe, and effective" alternative.

The SynAIRgy trial, which involved 646 patients, met its primary endpoint, delivering a 55.6% average reduction in AHI (apnoea-hypopnea index) over 26 weeks. The company now plans to submit a new drug application (NDA) to the US FDA in early 2026, with results from a second Phase 3 trial expected later this year.

The study chair of the SynAIRgy clinical trial, Patrick Strollo, Jr. MD, commented:

These Phase 3 topline results are highly encouraging and represent the potential for a much-needed innovation in the treatment of OSA. For too long, progress in OSA has been limited, leaving many people with OSA without sustainable treatment options.

The results from SynAIRgy suggest that if approved, AD109 could offer a compelling new treatment option — a novel oral drug that targets the neuromuscular root cause of airway obstruction in sleep apnea and holds promise for transforming care for a broad range of patients.

Why are investors worried?

While ResMed is widely regarded as the global leader in sleep apnoea therapy — with its CPAP devices and cloud-connected solutions used by millions — the success of a non-device-based treatment could introduce a new dynamic to the market.

However, it is worth remembering that ResMed remains deeply entrenched in the sleep apnoea market — both in terms of scale and clinical infrastructure.

The company continues to benefit from strong global brand and clinician trust, recurring revenue through device and SaaS models, a growing pipeline of cloud-connected solutions and data tools, and an unmatched distribution network.

It is also important to note that AD109 is still in the trial phase, with no regulatory approval yet in place. So, today's decline might prove to be a bit of an overreaction, but time will tell.