MoonLake Immunotherapeutics, Inc. (MLTX) delivered its strongest single-session rally in over a month on Tuesday, with shares jumping 11% as a major biotech-focused investment firm significantly rebuilt its position in the company. The move came alongside explosive retail trading activity on Stocktwits, fueled by takeover speculation and growing optimism around the company’s lead drug candidate, Sonelokimab.
Cormorant Asset Management Lifts Stake Above 6%
The catalyst behind Tuesday’s surge was a Schedule 13G filing that revealed Cormorant Asset Management had acquired 4.36 million Class A ordinary shares in MoonLake Immunotherapeutics, representing a 6.1% ownership stake as of December 31, 2025. This marks a significant increase from the approximately 2 million shares, or 3.14%, that Cormorant had disclosed in October 2025 filings — a period during which the firm had actually reduced its position below the 5% SEC reporting threshold.
Cormorant Asset Management is a biotech-specialized investment firm with a track record of backing high-conviction life sciences companies. Its current portfolio includes notable names such as Praxis Precision Medicines, BridgeBio Oncology Therapeutics, Edgewise Therapeutics, and Metsera — the latter of which was acquired by Pfizer last year. As of September 30, 2025, Cormorant held positions in 43 stocks, with an estimated portfolio value of approximately $1.45 billion, according to data from Quiver Quantitative. The firm’s decision to more than double its MoonLake stake signals strong conviction in the company’s pipeline and near-term catalysts.
FDA Momentum Builds Behind Sonelokimab
MoonLake’s regulatory outlook has steadily improved over recent weeks, adding credibility to the bullish case for MLTX. Earlier this month, the U.S. Food and Drug Administration (FDA) granted Fast Track designation to Sonelokimab, the company’s lead investigational therapy, for moderate-to-severe palmoplantar pustulosis. Fast Track status is designed to accelerate the development and review of drugs that treat serious conditions and fill an unmet medical need, a significant milestone for MoonLake and its investors.
In addition to the Fast Track designation, MoonLake recently confirmed that a Type B meeting with the FDA validated its clinical evidence strategy for Sonelokimab in hidradenitis suppurativa — a chronic and debilitating inflammatory skin condition with limited treatment options. Following this positive regulatory engagement, several brokerages responded by raising price targets or upgrading the stock. However, Goldman Sachs took a more cautious stance, downgrading MoonLake to ‘Sell’ last month and citing “high risk” around the drug’s approvability in hidradenitis suppurativa.
Despite the Goldman downgrade, market sentiment has broadly remained constructive. MoonLake is scheduled to host an investor day on February 23, where the company plans to provide detailed updates on the clinical development roadmap and regulatory pathway for Sonelokimab across multiple inflammatory disease indications. That upcoming event has added another layer of anticipation to this week’s price action.
Retail Traders Flood Stocktwits With Takeover Buzz
Adding further fuel to Tuesday’s rally was a dramatic shift in retail trader sentiment on Stocktwits. Sentiment for MLTX flipped from “extremely bearish” to “extremely bullish” within a single day, accompanied by a more than 900% surge in 24-hour message volume — an extraordinary spike that reflects just how quickly the mood around this stock has changed.
Retail traders pointed to the Cormorant filing as a fundamentally bullish signal. One user argued the filing had “broken” the bear thesis entirely, reasoning that Cormorant — a firm intimately familiar with the underlying science — would not have bought back in at prices between $12 and $16 unless it believed the negative narrative around the stock was wrong. Other users speculated that a press release or corporate announcement could be imminent ahead of the investor day.
Several traders flagged unusual post-market volume as evidence that institutional players may be accumulating shares. One particularly viral comment pointed to recent travel activity involving Merck’s corporate jet, with multiple reported trips to Zurich — where MoonLake is headquartered — stoking speculation about a potential acquisition by the pharmaceutical giant.
MLTX Rises 33% Year-to-Date
MoonLake’s stock has now risen approximately 33% since the start of 2025, reflecting sustained investor interest in the company’s pipeline progress and regulatory milestones. With the investor day approaching, FDA engagement accelerating, and a high-profile institutional investor doubling down on its position, MoonLake remains one of the more closely watched names in the mid-cap biotech space.
