Chinook marks an ignominious end for Sting

For a field that a few years ago was attracting deals worth hundreds of millions of dollars, Sting agonism has come to an ignominious end. After seeing disappointing results, Aduro, perhaps Sting’s foremost exponent, yesterday ran up the white flag and was reversed into by a private biotech called Chinook Therapeutics.

Perhaps the strangest aspect of this deal is that Aduro still has two deals in place for Sting, with Novartis and Lilly, and a separate anti-CD27 tie-up with Merck & Co, but has now put these “legacy programmes” up for disposal. Its focus turns instead to Chinook’s small pipeline of kidney disease projects.

The most advanced of these is atrasentan, a me-too version of Glaxosmithkline’s Letairis that should resume phase III development for IgA nephropathy in the second half. Atrasentan has a curious history, having first been discontinued by Abbvie, before its phase III Sonar study read out positively, according to a Lancet paper.

CHK-336, an investigational small molecule for treating an undisclosed ultra-rare kidney disease, is in preclinical development. The pipeline also includes Aduro’s own anti-April MAb BION-1301, whose development for multiple myeloma was stopped, and which is now in phase I for IgA nephropathy.

The ownership of the combined company, to be known as Chinook, will be 50/50, with Aduro securing such a relatively high stake largely on account of its existing cash balance, some $200m. Chinook is separately raising $25m to put into the mix, but to all intents and purposes this is a reversal into Aduro by Chinook, whose current management will control the combined business.

Though Aduro had not made much noise about it, the writing had been on the wall for its Sting programme for some time. In December a US SEC filing quietly disclosed that Novartis had removed from its pipeline ADU-S100, the lead asset under the firms’ groundbreaking 2015 Sting deal.

That deal had catapulted Sting into the spotlight as a novel immuno-oncology pathway (Pre-IPO Sting gives Novartis a stake in Aduro, March 30, 2015). More was to follow, as Lilly bought into Aduro’s Sting antagonist approach, Bristol-Myers Squibb paid $300m for the Sting player IFM Therapeutics, and Abbvie acquired Mavupharma for an undisclosed amount.

But all was not well, as clinical data fired blanks: Merck & Co’s in-house Sting agonist MK-1454 stunned attendees of the 2018 Esmo meeting with a 0% response rate as monotherapy, and ADU-S100 itself disappointed at Asco last year.

Based on the data Novartis decided to wind down ADU-S100 combo trials with spartalizumab and with Yervoy, while a Keytruda combo trial in first-line head and neck cancer continues to its second-half 2020 readout. In January Aduro revealed a restructuring, laying off 59% of its workforce.

And the rest?

If Aduro and Novartis have admitted that Sting is a dud, where does this leave the numerous other players? Abbvie, for instance, does not mention any specific Mavupharma assets in its pipeline.

On the other hand Bristol still lists Sting in its pipeline, and BMS-986301 is in an Opdivo/Yervoy combo trial slated to end in 2022. Eisai’s E7766, Glaxosmithkline’s GSK3745417, Spring Bank’s SB 11285 and Synbio’s SYNB1891 all recently started phase I – a paradoxical development given how the class has underwhelmed.

It is still possible for Aduro/Chinook to offload these types of assets to a start-up with a sufficient appetite for risk, but investors should perhaps not expect a massive windfall.