RNA specialist Ribo files $205m IPO in Hong Kong

Chinese RNA-based medicine developer Suzhou Ribo Life Science has filed a Hong Kong IPO, aiming to raise new funds for its lead RBD4059 drug candidate for thrombotic diseases.

The small-interfering RNA (siRNA) drug, which targets Factor XI, is in a mid-stage clinical trial involving patients with coronary artery disease in Sweden and has been billed as the first drug in the siRNA class to target thrombotic diseases.

Ribo's IPO is aiming to raise around HKD 1.59 billion (around $205 million) through the sale of 27.5 million shares at HKD 57.97 each, according to the prospectus (PDF) filed with the HKEX exchange in Hong Kong.

RBD4059 is designed to reduce the risk of clot formation, without increasing bleeding risks, and with dosing intervals that could be several months apart, according to Ribo.

That dosing profile could differentiate RBD4059 from other drugs targeting Factor XI, including oral candidates from Bayer (asundexian) and Bristol Myers Squibb/Johnson & Johnson (milvexian), and antibodies from Novartis (abelacimab) and MSD/Adimab (MK-2060).

In RBD4059's phase 1 clinical trial, no adverse safety signals were identified within the tested dose ranges, other than injection site reactions.

Ribo's approach has been to carry out discovery and early development work for its siRNA candidates in China, with simultaneous clinical testing in other countries, such as Sweden and Australia, to speed up their progress in international markets. Including RBD4059, its pipeline consists of seven clinical-stage assets spanning cardiovascular, metabolic, kidney, and liver diseases, four of which are in phase 2 testing.

RBD5044 is an siRNA targeting APOC3, a protein that plays a role in lipid metabolism, and is in a phase 2 trial in Sweden involving people with elevated blood triglycerides. Its closest competitor is Rona Therapeutics' RN0361, which is in mid-stage clinical testing for the prevention of pancreatitis in patients with severe hypertriglyceridaemia.

Its liver disease pipeline is headed by RBD1016, an siRNA targeting hepatitis B surface antigen (HBsAg) that Ribo hopes could achieve functional cure of chronic hepatitis B infections and is in phase 2 trials in China and Sweden.

Meanwhile, the biotech's RIBO-GalSTAR siRNA platform has also attracted partnerships with Boehringer Ingelheim and Qilu Pharmaceutica that are collectively worth more than $2 billion. The Boehringer alliance is focusing on metabolic dysfunction-associated steatohepatitis (MASH), while Ribo is working with Qilu on diseases associated with dyslipidaemia.

Trading in Ribo shares on the HKEX is scheduled to begin on 9th January, following a subscription period ending today.