Affibody Medical AB Files for IPO: A Pioneer in Bispecific Therapeutics with Over $800M in Strategic Partnerships

In 2022, a total of five bispecific antibody (hereinafter referred to as “bispecific antibodies”) drugs were launched globally, surpassing the cumulative total of the previous 12 years.

According to Frost & Sullivan data, the market size of the bispecific antibody industry was $2.5 billion in 2020, with an expected annual growth rate of 29.3% from 2024 to 2030. In the next 3–5 years, bispecific antibody drugs may enter a period of explosive market launches.

Affibody Medical AB (hereinafter referred to as “Affibody”) is a biopharmaceutical company focused on the research and development of novel bispecific antibody drugs. Founded in 1998, the company is a controlled subsidiary of Patricia Industries. Based on proprietary Affibody^®Leveraging its molecular and Albumod™ technology platforms, Affibody has developed a diverse pipeline, with izokibep as its lead candidate.

Leveraging its innovative pipeline of investigational candidates, Affibody has established collaborations with multiple biopharmaceutical companies.

In May 2020, Affibody and AcceGen Biotechnology entered into a global strategic collaboration agreement regarding Izokibep. Under the terms of the agreement, Affibody will receive a $10 million upfront payment and up to $215 million in regulatory and sales milestone payments. AcceGen Biotechnology obtained exclusive rights to develop and commercialize Izokibep in China, South Korea, and other countries, as well as the right to conduct clinical development in the Asia-Pacific region excluding Japan.

In March 2023, Affibody entered into a collaborative licensing agreement with the Italian biopharmaceutical company Chiesi. Chiesi will provide Affibody with investments of up to $637 million to develop and market innovative inhaled therapies for respiratory diseases using Affibody’s proprietary technology.

Affibody molecules are artificial protein molecules derived from the B domain of Staphylococcal Protein A (SPA), with a molecular mass of approximately 6.5 kDa. Thirteen specific sites within the helical structure of the affibody can be randomly mutated to generate an affibody library that theoretically binds to any target protein molecule. Screening this library yields affibodies that bind with high specificity to a particular target protein.

Affibody molecules exhibit binding characteristics to target proteins that are similar to those of antibodies; however, they offer several unique advantages over antibodies. They can be obtained through in vitro screening and produced on a large scale via chemical synthesis or prokaryotic expression. Affibodies feature low molecular weight, strong tissue penetration in vivo, high plasma clearance rates, and favorable physicochemical stability. Furthermore, they can be conjugated with labeling molecules (such as fluorescent proteins, biotin, etc.) through cross-linking or fusion expression without compromising their binding affinity for target protein molecules.

Therefore, Affibody is particularly suitable for molecular targeted therapy of tumors and in vivo molecular imaging diagnosis.

Leveraging the advantages of affibodies, Affibody has developed a novel antibody mimic—Affibody.^®Molecules with superior properties to monoclonal antibodies (mAbs) and antibody fragments. With a molecular weight of only 6 kDa, they exist in an inert form (lacking an Fc fragment) and can specifically bind to a wide range of target proteins. Furthermore, their inherent Affibody characteristics enable drug development through multispecific constructs, potentially yielding candidate drugs with enhanced efficacy.

Currently, Affibody^®Secured over 30 patents and successfully registered in the European Union, the United Kingdom, Switzerland, the United States, Japan, Australia, China, and other countries.

Despite compared with traditional antibodies, Affibody^®Possesses multiple advantages, yet it still has its own drawbacks. Due to its small molecular weight and lack of an Fc fragment, Affibody^®It is readily filtered by the glomeruli and excreted by the kidneys, lacks FcRn-mediated recycling, and is susceptible to lysosomal degradation in target cells; these characteristics result in a short half-life (typically only 2 hours).

To address this drawback, Affibody created the Albumod™ platform, which comprises over ten billion Affibody molecules^®Molecular composition; these molecules all possess unique binding sites that can bind to specific targets. Leveraging the Albumod™ technology, Affibody has developed Affibody^®Binds to serum albumin, increasing its molecular weight and leveraging the recycling mechanism of FcRn to extend its half-life, thereby achieving a dosing interval comparable to that of antibody drugs.

Research on Affibody has demonstrated that small-sized Affibody^®The molecule can be formulated into an ideal subcutaneous preparation, with a dose per injection volume 10 times higher than that of mAbs. Additionally, due to the small size and stability advantages of the molecule, Affibody^®It can also be administered via other routes, such as inhalation.

Currently, Affibody has established multiple clinical pipelines, with Izokibep as its lead candidate drug.

Izokibep, co-developed by Affibody, Trianni Biopharma, and antibody drug developer Acelyrin, is a novel bispecific fusion protein therapeutic that effectively targets interleukin-17A (IL-17A) and serum albumin. It exhibits an antibody-like half-life and may accumulate at disease sites via albumin binding. Furthermore, its molecular weight (18 kDa) is approximately one-eighth that of conventional antibodies, and its apparent affinity for IL-17A is roughly 1,000 times higher than that of typical anti-IL-17A antibodies.

Therefore, subcutaneous administration of izokibep can achieve drug absorption levels comparable to those of conventional antibody drugs that require intravenous infusion. Furthermore, its lower molecular weight enables superior penetration into target tissues that are typically inaccessible to traditional antibodies, such as the skin, joints, and eyes, thereby enhancing therapeutic efficacy.

Notably, Izokibep is produced in an *E. coli* system, and Affibody estimates that its production cost per dose at commercial scale may be lower than that of typical antibody drugs produced in mammalian cell lines.

To date, izokibep has been evaluated in clinical trials for multiple indications, including hidradenitis suppurativa (HS), psoriatic arthritis (PsA), axial spondyloarthritis (axSpA), and uveitis.

Phase I first-in-human clinical trial results for Izokibep showed no safety concerns in healthy volunteers and patients with psoriatic arthritis (PsA). All PsA patients exhibited a rapid response after a single dose, with further improvement in efficacy observed in those receiving multiple doses.

Clinical results have demonstrated that the drug is well tolerated, with a safety profile consistent with that of anti-IL-17A agents. To date, nearly 500 patients have received treatment with izokibep, the majority of whom have been on therapy for more than three years.

In March this year, Akeso Biopharma presented clinical Phase IIb/III study data on Izokibep for the treatment of moderate-to-severe hidradenitis suppurativa (HS) at the American Academy of Dermatology (AAD) Annual Meeting. The study enrolled a total of 30 subjects across nine centers in the United States. Participants received weekly subcutaneous injections of 160 mg of Izokibep and were divided into two cohorts: Cohort A (open-label trial) and Cohort B (randomized, double-blind, placebo-controlled study).

Results from Group A demonstrated a significant increase in the Hidradenitis Suppurativa Clinical Response (HiSCR) among patients after 12 weeks of treatment with izokibep. The data showed that the proportions of patients achieving at least 50% (HiSCR50), 75% (HiSCR75), 90% (HiSCR90), and 100% (HiSCR100) reduction in abscesses and inflammatory nodules were 71%, 57%, 38%, and 33%, respectively. To date, no other medication has achieved such favorable efficacy within this treatment timeframe.

The clinical safety data from this study are consistent with those from previous izokibep studies and the overall safety profile of IL-17A antagonists. The most common adverse events were mild-to-moderate injection site reactions (ISRs). No cases of candidiasis were reported, and there was no evidence of an increased risk of infection following treatment.

Currently, Affibody, in collaboration with Chuanxiang Bio and Acelyrin, is continuing to evaluate izokibep for hidradenitis suppurativa (HS), psoriatic arthritis (PsA), and uveitis, with primary data from the Phase IIb/III clinical trial for PsA expected in the first quarter of 2024.

Although China started relatively late in the development of bispecific antibodies, momentum is strong. As domestic companies’ bispecific antibody technology platforms mature, the variety of approved bispecific antibody drugs will continue to increase, and China’s bispecific antibody market will expand rapidly.

According to the report “Special Topic on Innovative Drugs: Bispecific Antibodies at the Forefront, Advancing at Double Speed” released by Southwest Securities, the market size of bispecific antibodies in China is projected to reach $10.8 billion by 2030, with a compound annual growth rate (CAGR) of 81.7% from 2022 to 2030. Currently, more than 30 biopharmaceutical companies in China have established pipelines for bispecific antibody drugs, with over 300 bispecific antibody candidates under development and nearly 100 having entered clinical trials.

Currently, three bispecific antibody drugs have been approved for marketing in China: Amgen’s Blinatumomab, Roche’s Emicizumab, and Akeso’s Cadonilimab. Among them, Cadonilimab is the first tumor-targeting bispecific antibody against dual immune checkpoints independently developed by an innovative Chinese biotechnology company.

Meanwhile, competition among domestic bispecific antibody companies has reached a fever pitch. According to data from the Patsnap Global New Drug Intelligence Database, 193 bispecific antibodies have been approved for clinical trials in China, with 17 of them having entered Phase III clinical trials, including Akeso’s AK112, Alphamab Oncology’s KN046, BeiGene’s ZW25, and Genrix Biopharma’s GR1801.

In addition, key bispecific antibody pipelines of Innovent Biologics, Zeltis Biosciences, YZY Biopharma, and Sichuan Baili have all advanced to Phase II clinical trials. Innovative companies such as Hanxiong Biotech, Lüzhu Biopharma, and Shenghe Biotech have also entered the bispecific antibody sector, with their investigational pipelines progressing to Phase I clinical trials.

From the perspective of indications for bispecific antibody development in China, oncology indications account for over 90%, with lung cancer being the primary focus of corporate R&D, followed by other common malignant tumors such as lymphoma, gastric cancer, and breast cancer. Furthermore, bispecific antibody development has expanded into areas including autoimmune diseases, ophthalmic disorders, and rare diseases.

As the golden age of bispecific antibodies dawns, numerous innovative pharmaceutical companies are entering the fray, and we may see the emergence of more bispecific antibody drugs in the future.