MLTX Stock On Track For Worst Week Since Last Fall As FDA Filing Date For Skin Disease Drug Draws Near

• MoonLake plans to file with the U.S. Food and Drug Administration (FDA) by the end of September, seeking permission to sell sonelokimab for hidradenitis suppurativa. 
• By late November, the FDA should say whether it accepted the filing, whether it will review it faster, and when it will decide.
• Three shots are already approved for HS: AbbVie’s Humira, Novartis’s Cosentyx, and UCB’s Bimzelx.

Shares of MoonLake Immunotherapeutics (MLTX) slid about 15% this week as investors marked down the stock weeks before a planned U.S. filing for its lead drug.

MLTX  has faded since a mid-June rally on year-long hidradenitis suppurativa data and an August psoriatic arthritis readout, leaving the stock about 80% below its 52-week high. The stock is on track to clock its worst week in about a year, if losses hold.

Filing Date Looms

MoonLake plans to file with the U.S. Food and Drug Administration (FDA) by the end of September, seeking permission to sell sonelokimab for hidradenitis suppurativa, a painful condition that causes boils and tunnels under the skin. The request would cover both adults and teens. The agency has already said the existing studies can support a filing.

By late November, the FDA should say whether it accepted the file, whether it will review it faster, and when it will decide. A standard review would point to a possible U.S. launch in the second half of 2027.

What The Drug Did In Trials

Sonelokimab is an experimental injection that blocks two proteins that drive inflammation. After one year in two late-stage studies, about two-thirds of adults had a large drop in skin lesions and about one-third saw their lesions disappear. Early data in teens looked similar. Safety matched earlier studies.

Doubt remains because the first look at the data, at four months, was mixed. One study succeeded. The second missed its main goal after patients on dummy treatment improved more than expected, a setback that crushed the stock a year ago. The FDA, however, later said MoonLake did not need new skin-disease trials.

In August, a late-stage study of the drug in patients with psoriatic arthritis also hit its main goal.

A Crowded Market

Three shots are already approved for HS: AbbVie’s Humira, Novartis’s Cosentyx, and UCB’s Bimzelx. Other new drugs are also in development.

MoonLake says its drug design and long-term trial results can help it stand out, but it would enter a market where rivals already have years of real-world use.

Next Catalysts

MoonLake ended June with $537 million in cash, enough, it says, to last into mid-2028. It has no approved product and lost $131.5 million in the first half of 2026.

The nearest catalyst for the stock is the hidradenitis filing. A second late-stage joint-disease study should finish enrolling this quarter, with results later this year. MoonLake also plans to start a late-stage trial in palmoplantar pustulosis, which has no approved U.S. treatment.

How Did MLTX Retail Traders React?

On Stocktwits, retail sentiment around MLTX stock stayed ‘neutral’ over the past 24 hours, while message volume was ‘high.’

A Stocktwits user said that shorts are resorting to bashing the company for its perceived lack of announcements, as they have no arguments against its drug.

Another user opined that even with approval for sonelokimab, the company will enter a crowded market. “Yes the pie is big but it will  be divided into many little pieces. $20 is already a lot for this company,” they wrote.

Certain analysts, however, are more bullish. Last month, H.C. Wainwright raised the firm's price target on MoonLake Immunotherapeutics to $50 from $45 and kept a Buy rating on the shares after increasing its probabilities of approval to 70% from 60% in hidradenitis suppurativa, to 60% from 50% in psoriatic arthritis, and to 50% from 40% in axial spondyloarthritis.

MLTX stock has fallen 3% year-to-date. 

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