Reeling from Covid flop, Icosavax says its RSV candidate passed early test. But investors need some more convincing
Three months separated from a disappointing readout of its Covid-19 vaccine, Icosavax is back with what it calls positive topline data for a different VLP vaccine candidate — although investors aren’t impressed.
IVX-121, a vaccine candidate for respiratory syncytial virus (RSV), appeared to generate “robust” immune responses among both young and older adults, as measured by neutralizing antibodies, and appeared generally well-tolerated, Icosavax reported.
The interim Phase I/Ib results offer key proof of concept for the Seattle-based biotech’s foundational virus-like particle platform technology, said CEO Adam Simpson. VLP is spontaneously assembling proteins that Icosavax co-founder and synthetic biology researcher Neil King previously described as akin to soccer balls in shape.
“They also reaffirm our strategy to combine multiple pathogen targets in one vaccine,” he said in a statement. “As planned, Icosavax will now progress development of IVX-121 combined with a human metapneumovirus (hMPV) VLP, as our IVX-A12 bivalent vaccine candidate.”
RSV and hMPV are two leading causes of pneumonia, he added, and neither has an approved vaccine.
Icosavax licensed a prefusion stabilized form of the RSV F antigen from the NIH. But its plan, spelled out in an S-1 when it went public last year, has always been to forego a monovalent shot in favor of a 2-in-1 vaccine.
In a note, Cowen’s Phil Nadeau noted the neutralizing antibody titers generated by IVX-121 — up to 7,687 IU/mL for the younger group and up to 7,561 IU/mL for the older group — “are in the range of those produced by Pfizer’s RSV vaccine candidate PF-06482077 (RSVpreF) and GSK’s RSVpreF3 OA, suggesting that Icosavax has a viable RSV component for its RSV+hMPV vaccine.”
Roger Song at Jefferies also gave the data a thumbs-up:
While investors may think nAb GMFR is generally comparable to comps’ (slightly lower in older population) thus unclear the market positioning given late to market, we see Co’s vaccine could be differentiated in multiple fronts, supported by today’s preliminary data: 1) no drop off in nAb titer from young to older adults, 2) very benign reactogenicity/tolerability, 3) wide window for combo vaccine given equivalent immunogenicity at the lowest dose and favorable AE at the highest dose.
Nonetheless, shares are down about 14% in pre-market trading, putting the stock price at $7.27.
In addition to its vaccine, Icosavax also tested an aluminum hydroxide adjuvant in the trial to make sure it didn’t work, as it’s failed in other companies’ studies before. And investigators found that the adjuvant did not make a difference.
The company plans to file an IND and start a Phase I trial for IVX-A12 in the second half of the year.