Palatin Technologies Inc. (PTN) shares jumped 8.41% to $27.77 in after-hours trading Wednesday, following a regulatory filing that revealed significant institutional interest in the small-cap biotech.

The stock had closed regular trading at $25.62, down 6.84% for the day, before reversing course after the bell.

What Triggered the Move

Janus Henderson Group plc filed a Schedule 13G with the Securities and Exchange Commission, a form passive investors use when they accumulate more than 5% of a company's stock. The filing, dated Nov. 28 and officially signed Monday, shows Janus Henderson now owns 170,097 shares representing 9.99% of Palatin's common stock.

That ownership figure includes pre-funded warrants and common warrants exercisable within 60 days, though it's subject to a 9.99% beneficial ownership limitation.

Here's where it gets interesting: Janus Henderson Biotech Innovation Master Fund Ltd, a subsidiary of Janus Henderson Group, holds 118,196 of those shares on its own, representing 6.6% of the company. According to the SEC filing, both entities report shared voting and dispositive power over their holdings, meaning neither has sole authority to vote or dispose of the shares independently.

The Warrants Left on the Table

The filing also disclosed that an additional 8,562 pre-funded warrants, 182,000 Series J common warrants, and 182,000 Series K common warrants were excluded from the reported figures due to the ownership cap. That's a substantial amount of potential shares being left out of the calculation.

Kristin Mariani, Head of North America Compliance and Chief Compliance Officer at the New Jersey-based biopharmaceutical company, signed the filing.

A Volatile Trading Picture

Palatin Technologies has experienced dramatic swings this year. The stock has rebounded an impressive 388% over the past six months, though it remains down 60.58% year to date. With a market capitalization of just $45.77 million, the company trades in a wide 52-week range of $7.25 to $72.50.

The institutional vote of confidence from Janus Henderson appears to be giving investors renewed optimism about the biotech's prospects, at least for now.