SLS Stock Notches 3-Week Winning Run: MassMutual Opens Tiny Stake Ahead Of Key AML Readout

• MassMutual disclosed a tiny new stake of 24 SLS shares, valued at $354.24.
• Investors remain focused on Sellas’ Phase 3 Regal AML trial, which is at 78 of 80 events needed for final analysis.
• CEO Angelos Stergiou’s Fourth of July post and references to “strategic partners” fueled fresh retail buyout chatter.

Shares of Sellas Life Sciences (SLS) logged its third consecutive weekly gain last week after fresh institutional ownership data showed that MassMutual Private Wealth & Trust opened a small new position ahead of the company’s closely watched acute myeloid leukemia (AML) trial readout.

SLS stock rose 21% last week after a rally that included a 13% surge on Thursday. But shares are down 1% overnight late Sunday. 

MassMutual Opens Small SLS Position

According to data from Quiver Quantitative, MassMutual Private Wealth & Trust, FSB disclosed ownership of 24 SLS shares as of June 30. The stake was valued at $354.24 and was reported on July 2. MassMutual’s 13F filing disclosed 2,495 stock positions with total holdings of $3.84 billion. Its largest holdings included Apple, Nvidia and Visa.

The same Quiver data also showed that First Financial Bank held 10,000 SLS shares, valued at $147,600, as of June 30. The stake was reported last week. 

The central focus for SLS investors remains the company’s Phase 3 Regal trial of GPS, or galinpepimut-S, in AML. The trial has reached 78 of the 80 events required to trigger its final analysis, putting Sellas close to one of the most important clinical readouts in its history. Sellas CEO Angelos Stergiou has called the slower-than-expected event accumulation an encouraging sign.

Sellas has previously said the Regal trial would be considered successful if GPS extends median overall survival to 12.6 months, compared with 8 months under standard treatment.

SLS Retail Traders Watch For Buyout Signs

Sellas has also remained a focus among retail investors looking for possible buyout or partnership clues. Stergiou’s Fourth of July LinkedIn post also became fresh fodder for retail buyout chatter. In the message, the CEO said: “To our clinical investigators, research sites, collaborators, strategic partners, and shareholders: Thank you for your trust, your partnership, and your continued belief in our vision. Meaningful innovation is never achieved alone,” adding that he was “incredibly optimistic about the future.” 

Investors are also parsing Sellas’ updated executive severance and change-of-control arrangements. Stergiou’s amended agreement shifts certain change-of-control severance payments to a lump sum. CFO John Burns and Chief Development Officer Dragan Cicic would receive 15 months of base salary, target bonus payments, COBRA reimbursement and full equity acceleration under qualifying change-of-control terminations.

The company’s market cap has grown from $73 million at the start of 2024 to more than $1.5 billion by mid-2026. Sellas also ended the first quarter with $107.1 million in cash and raised another $28.7 million through warrant exercises in April and May.

Shareholders recently approved a 20 million-share increase to Sellas’ 2023 Equity Incentive Plan. Stergiou was also awarded 1.065 million restricted stock units, vesting over four years. Following the grant, his ownership increased to 1.76 million shares.

How Do Retail Traders Feel About SLS?

On Stocktwits, retail sentiment for SLS has been ‘extremely bullish’ since a week amid ‘high’ message volume.

One user said, “$SLS 80th news possibly this week, possibly Monday pre market”

Another user said, “$SLS I liked it at $3, I liked it at $8, I still like it at $15. Still cheap compared to BO price, IYKYK.”

SLS stock has surged 607% over the past year. 

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