Share in cystic fibrosis firm Sionna rise sharply after IPO
Sionna Therapeutics has closed its initial public offering, raising $191 million for its pipeline of therapies for cystic fibrosis (CF), which offer a different mechanism to those sold by market leader Vertex Pharma.
The Waltham, Massachusetts-based biotech sold 10.6 million shares at $18 apiece – at the upper limit of its price predictions – and also raised the number on offer by 1.8 million. The stock, which trades under the SION symbol on the Nasdaq, rocketed almost 40% to reach $25 on its debut.
It is the fourth US biotech to go public since the start of this year after Ascentage Pharma, Metsera, and Maze Therapeutics.
Sionna is focused on developing CF therapies that normalise the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, whose gene is defective or missing in patients with the genetic disorder.
They are designed to stabilise the nucleotide-binding domain 1 (NBD1) of CFTR, a different approach to the exon-skipping therapies sold by Vertex Pharma for CF, which use antisense oligonucleotides to splice sites out of the RNA coding for CFTR, stripping out mutations and resulting in a truncated but functional protein.
Vertex's CF therapies account for the bulk of its revenues and are predicted to reach $10 billion in 2024, driven by triple therapy Trikafta/Kaftrio (elexacaftor, ivacaftor, and tezacaftor), which provides a treatment option for up to 90% of CF patients. Sionna's chief medical officer – Charlotte McKee – was formerly head of CF therapy clinical development at Vertex.
Sionna reckons its approach could improve on the efficacy of Vertex's blockbusters, as around two-thirds of patients taking the exon-skipping therapies don't get full restoration of CFTR function. It is adopting a similar approach of using combinations of its NBD1 stabilisers to cover as many patients with CF as possible.
The IPO will fund ongoing phase 1 and future phase 2a proof-of-concept testing of a pair of compounds, with the latter trials due to start in the second half of 2025, and will also go towards building manufacturing capacity.
The biotech is also running clinical trials of complementary CFTR modulators, three of which have been licensed from AbbVie, headed by galicaftor, which targets CFTR's transmembrane domain 1 (TMD1) and has completed a phase 2 study.
Formed in 2019, Sionna's most recent financing was a $182 million third round that closed last year, which followed a $111 million Series B in 2022.
