Acelyrin, MoonLake rivalry heats up as both chase blockbuster PsA market

The rivalry between Acelyrin (NASDAQ:SLRN) and MoonLake Immunotherapeutics (NASDAQ:MLTX) is heating up, with both expected to release potentially market-moving data in the next few months for their respective drugs to treat psoriatic arthritis, a market opportunity that could be worth more than $10B.

Acelyrin and MoonLake have both developed IL-17 inhibitor therapies to treat the skin disorder hidradenitis suppurativa, or HS, and psoriatic arthritis, or PsA, a type of arthritis that affects people with psoriasis. In the wake of a failed Acelyrin study, MoonLake now appears to have the upper hand in HS, but the jury is still out for PsA.

Both stocks had been feeding off each other over the last few months. Shares of MoonLake soared 78% on June 26 after it reported positive Phase 2 data for its drug sonelokimab, or SLK, in the treatment of HS. Investors rewarded Acelyrin as well, pushing shares 35% higher. Acelyin made its market debut in May.

Acelryin was brutally punished on Sept. 11, however, when it reported that a Phase 2b/3 study for its drug izokibep in the treatment of HS failed to meet its primary endpoint at week 16. The stock began tumbling in after-hours trading and finished the Sept. 12 session 54% lower. MoonLake shares, meanwhile, rose 10%.

“Izokibep is now in the rearview in HS, clearing the way for SLK to likely emerge as the preferred biologic in HS,” wrote BTIG analyst Julian Harrison in a recent note, who has a buy rating on MoonLake.

The drugs will face off again in the next several weeks, this time in the treatment of PsA, with MoonLake expected to report topline Phase 2 data on SLK in the first half of November and Acelyrin slated to report topline Phase 2b/3 data for izokibep in Q1 2024. MoonLake is also expected to release additional Phase 2 results for SLK in HS in mid-October, according to analysts.

There’s also a third horse in the race: UCB’s bimekizumab, or BZK. Like SLK and izokibep, BZK is also an IL-17 inhibitor. The drug is already marketed in the EU under the brand name Bimzelx for plaque psoriasis, PsA and axial spondylarthritis.

UCB filed for EU approval of BZK for HS in July. The company has also filed to have the drug approved in the US for plaque psoriasis, with a decision expected in Q3, according to a UCB statement in late June.

According to Needham, SLK is expected deliver “at or above the best-in-class results achieved by bimekizumab” when MoonLake releases Phase 2 data in early November.

As for Acelryin, the failure of its Phase 2b/3 study for HS “should not have any read-throughs to the PsA trial, but rates of discontinuations and adverse events related to injection site reactions at higher izokibep doses will be of interest,” according to Needham analyst Serge Belanger.

In a note released Sept. 13, Morgan Stanley said that while it still views Acelyrin as a “high potential” inflammation and immunology platform, it believes upcoming data from MoonLake in October and November “may present an overhang on SLRN shares.” The bank lowered its rating to equal weight, citing uncertainty on izokibep in HS.

“We therefore see a cleaner set-up for SLRN once this data flow is passed and the hurdle for izokibep in PsA is better established,” said Morgan Stanley analyst Vikram Purohit in his note. “Generally, we see a clean and successful PsA readout in Q1 2024 as the next key milestone for re-instilling investor confidence.”

Needham projected the current market opportunity for HS, psoriasis, PsA and a related condition called axial spondylarthritis at around $30B, reaching as high as $50B by the mid-2030s. It noted that MoonLake has estimated the current psoriatic arthritis market at around $6B, with potential to grow to $10B+ post-2030.

According to a Needham note dated Aug. 31, SLK demonstrated “best-in-class” potential and superior efficacy against two leading biologics to treat the conditions, namely Novartis’s (NVS) Cosentyx for psoriasis and Abbvie’s (ABBV) Humira for HS. Needham currently has a buy rating on MoonLake.

BTIG is also bullish on MoonLake for psoriatic arthritis.

“We see a good chance of SLK emerging as a preferred treatment option in PsA and there is likely minimal credit in MLTX shares now for this additional blockbuster market opportunity beyond HS,” said BTIG analyst Julian Harrison in a note dated Sept. 12.

Not surprisingly, speculation has been growing over whether MoonLake will be bought and by whom, especially after Reuters reported in mid-July that the biotech had been working with a bank on a possible sale.

“We believe SLK ticks off all the major boxes as an attractive M&A candidate,” said Needham’s Belanger in a note dated Aug. 31, adding that they see large pharma companies who already have biologics in the space, such as Abbvie (ABBV), Johnson & Johnson (JNJ), Eli Lilly (LLY) and Novartis (NVS), as “the most likely buyers of MLTX.”

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