The US FDA has accepted a supplemental Biologics License Application (sBLA) for onabotulinumtoxinA to improve the appearance of masseter muscle prominence. The filing, submitted by Allergan Aesthetics, an AbbVie company, moves the best-known botulinum toxin in medicine one step closer to an aesthetic indication in the lower face.

The acceptance is procedural, not an approval. It means the agency found the submission complete enough to review. A decision would make onabotulinumtoxinA — marketed as Botox and Botox Cosmetic — the first product specifically labeled for masseter muscle prominence in the United States.

What is masseter muscle prominence?

The masseter is the powerful chewing muscle at the angle of the jaw. When it enlarges, the lower face widens and the jawline appears square. Patients often report it as a cosmetic concern rather than a medical one.

Clinicians have treated it off-label with botulinum toxin injections for years. The procedure is among the most common off-label uses of neurotoxins in aesthetic practice, particularly in Asian markets, where a softer, narrower jaw contour is a frequent treatment goal. An approved labeling would give physicians dosing guidance, safety data and a legitimate basis for the injection that many already perform.

How does the review process work?

An sBLA asks the FDA to expand the uses of an already-approved biologic. OnabotulinumtoxinA has a long regulatory track record across therapeutic and aesthetic indications. Adding masseter prominence would extend that label into facial shaping rather than line smoothing.

Acceptance starts the clock on review. The agency will evaluate efficacy and safety data for the new indication before any decision. No approval timeline was disclosed in the announcement.

Why does labeling matter for off-label use?

Off-label treatment is legal and common. But it carries practical frictions for practices. Manufacturers cannot promote off-label uses, payers rarely cover them, and dosing rests on individual clinician experience rather than labeled guidance.

An approved indication changes that equation. It typically brings:

• Formal dosing and administration instructions for the masseter muscle
• Pivotal-trial safety and efficacy data specific to the indication
• A defensible basis for manufacturer communication and training
• Potentially cleaner documentation for record-keeping and consent

For dermatologists and aesthetic physicians, the practical difference is confidence — labeled data replaces anecdote at the injection point.

What's the market context?

Botox Cosmetic is the most-studied botulinum toxin in aesthetics, with approvals spanning glabellar lines, lateral canthal lines and forehead lines. A masseter indication would push it beyond wrinkle treatment into facial contouring, a category that has grown steadily as patients seek structural change rather than line reduction.

Competition is also part of the picture. Multiple neurotoxins now compete in the US aesthetic market, and manufacturers are differentiating on duration, onset and — increasingly — expanded indications. A first-in-class label for masseter prominence would be a differentiator no rival currently holds.

The size of the opportunity is hard to pin down. Off-label masseter treatment volume is not tracked in any single registry, but its persistence in clinical practice despite no label signals durable demand.

What comes next?

Physicians should watch the review closely. An approval would formalize a technique many already use, standardize expectations around results, and likely expand patient awareness of jawline contouring as a treatable concern. Until the FDA decides, masseter injections remain off-label, and practices should continue documenting consent accordingly.