As respiratory diseases enter their peak season, discussions about "Respiratory Syncytial Virus (RSV)" continue to surge across major social media platforms. According to surveillance data released by China's Center for Disease Control and Prevention on October 9 for the 40th week of this year, RSV ranked second in positive detection rates among respiratory samples from both outpatient influenza-like illness cases and hospitalized severe acute respiratory infection cases at sentinel hospitals.

Against the backdrop of persistently high RSV incidence, the market potential for prevention and treatment continues to expand, triggering an intense pharmaceutical development race in this sector, showcasing fierce competition among numerous players.

Behind this race lies multiple strategic battles: competition for first-mover market advantages, direct confrontation over clinical data and regulatory approval timelines, and positioning battles for specific demographic markets.

**Market Expansion Creates Blue Ocean Opportunities**

RSV is a widespread and contagious enveloped RNA virus that causes respiratory diseases. Children, adults aged 60 and above, and immunocompromised individuals are particularly susceptible, with infection rates reaching 90% among infants under two years old. RSV infections initially typically affect the upper respiratory tract with symptoms similar to common colds, but without proper treatment, they may progress to more severe lower respiratory tract infections, potentially leading to chronic respiratory and pulmonary diseases.

Statistical data shows that in 2024, the global number of RSV infection cases among children under five reached 91.4 million, with China accounting for 13.4 million. During the same period, global RSV infections among adults aged 65 and above totaled 46.5 million, with China representing 12.2 million cases.

Zhang Jing, Deputy Director of the Department of Respiratory and Critical Care Medicine and Director of the Chronic Airway Disease Subspecialty at Zhongshan Hospital affiliated with Fudan University, explained that RSV epidemic seasons vary geographically in China. Most provinces, particularly northern regions, experience peaks during winter and spring, with epidemic peaks concentrated from December to March of the following year, while southern regions may also see outbreaks during summer and autumn. The virus is highly contagious, primarily spreading through respiratory secretions and droplets, with one infected person capable of transmitting the virus to an average of 1.3-2.6 people in completely susceptible populations.

Currently, no specific antiviral drugs targeting RSV have been approved globally, with existing interventions primarily focused on symptomatic treatment.

Clinically, the broad-spectrum antiviral drug ribavirin is the only approved medication for RSV treatment. Zhang Jing explained that after entering RSV-infected cells, ribavirin rapidly phosphorylates, and its products competitively inhibit viral synthesis enzymes, thereby suppressing viral RNA and protein synthesis and replication. However, this drug has adverse effects including hemolytic anemia and decreased hemoglobin levels, and currently lacks sufficient evidence to prove its effectiveness in treating RSV infections. Considering the risk-benefit ratio, it is only recommended for severe pediatric patients and not for routine antiviral treatment of RSV lower respiratory tract infections in other patient types.

Given that no specific drugs are currently available for RSV, the prevention and treatment field is viewed as an undeveloped "blue ocean market" with enormous development potential and opportunities.

According to Frost & Sullivan report data, the global RSV prevention drug market (excluding RSV vaccines) was valued at approximately $2.7 billion in 2024 and is expected to reach $5.3 billion by 2035. In the Chinese market, with more prevention products expected to launch, the domestic RSV prevention drug market is anticipated to gradually expand starting from 2025.

In the RSV treatment drug market, the global market size is projected to reach $8.6 billion by 2035, while the Chinese market is expected to achieve significant growth during the same period, expanding to 4.5 billion yuan.

Miao Tianyi, Executive Partner at Simplicity Capital, stated: "The development direction of the RSV market at this stage is very clear, namely 'coordinated efforts in prevention and treatment, with key focus on elderly and infant populations.' The next five years will undoubtedly enter a period of rapid growth. On the policy front, both globally and in China are promoting favorable measures such as medical insurance reimbursement. From an industry perspective, the focus is gradually shifting from 'treatment-oriented' to 'prevention-oriented.' Companies that can excel in technological innovation and position themselves in emerging markets will be able to seize development opportunities."

**Monoclonal Antibodies Dominate RSV Prevention with Multiple Products Competing**

The continuous expansion of market size has further accelerated commercialization in the RSV prevention and treatment field. Currently, this sector has gradually established a competitive landscape with three core technological approaches: monoclonal antibodies, small molecule antiviral drugs, and vaccines. Among these, monoclonal antibodies, as passive immunization methods, are the preferred choice for enterprise development.

To date, three RSV prevention drugs have been approved globally: palivizumab developed by MedImmune (AstraZeneca), clesrovimab from Merck, and nirsevimab jointly developed by AstraZeneca and Sanofi, all targeting infant populations.

Among these, the earliest approved palivizumab has limitations including short prevention duration (requiring monthly injections during epidemic seasons) and narrow patient coverage (applicable only to high-risk infants), while the latter two are fully human monoclonal antibodies with core selling points of "long-acting + single dose," requiring only one injection per epidemic season.

In terms of sales performance, palivizumab and nirsevimab achieved global sales of $501 million and €1.686 billion (approximately $1.96 billion) respectively last year.

Notably, nirsevimab received approval from China's National Medical Products Administration in January 2024 for preventing lower respiratory tract infections caused by RSV in newborns and infants. In July of the same year, nirsevimab officially began commercialization in the Chinese market.

Recently on social media platforms like Xiaohongshu, numerous parents have posted about encountering shortages when trying to vaccinate their children with nirsevimab.

Regarding this situation, inquiries made to community health service centers across multiple districts in Shanghai revealed that most institutions responded that they currently do not have this antibody available for vaccination as they are not pilot hospitals.

However, when turning to hospitals for consultation, Shanghai Children's Medical Center indicated that nirsevimab is adequately stocked and available for immediate appointment scheduling, with prices calculated based on the child's weight: 1,876 yuan per dose for children under 5kg, and 3,184 yuan per dose for children over 5kg. The premium private hospital United Family Healthcare stated that some locations require appointments extending to mid-October, while other locations have relatively sufficient inventory due to new arrivals.

According to information gathered, Shanghai initially opened seven hospitals for nirsevimab registration last year, and this year further expanded the pilot scope by adding 36 medical institutions. Currently, the product's use covers public hospitals, private hospitals, and community health service centers.

Beyond imported products, multiple domestic companies are currently accelerating RSV monoclonal antibody development, with representative products including TNM001 from Tanmo Bio, RB0026 from RayBio, AK0610 from Akeso, and GR2102 injection from Chongqing Genrix Biopharmaceutical Co.,Ltd. (688443.SH). Among these products, TNM001 and RB0026 are the most advanced in development, both having reached Phase III clinical trials.

According to Tanmo Bio's prospectus, TNM001 is potentially the third globally and first domestically applicable long-acting anti-RSV prevention monoclonal antibody for both healthy and high-risk infants. Its Phase IIb clinical trial results showed that the drug achieved 66.2% protective efficacy against medically attended RSV-positive lower respiratory tract infections (RSV LRTI) and 82.3% protective efficacy against hospitalized RSV LRTI. The product's clinical trial application in the United States has also been approved.

Regarding RB0026, previous reports indicated that RayBio will invest 2 billion yuan in total for the product's development.

**Small Molecule Drugs and Vaccines Face Breakthrough Challenges as Companies Tackle Hard Problems**

Compared to the scalable breakthroughs achieved by monoclonal antibody products, the development of small molecule antiviral drugs for RSV treatment appears relatively limited.

Currently, the most advanced product is Akeso's RSV fusion protein small molecule inhibitor ziresovir (development code AK0529), which was licensed from Roche. In August this year, Akeso submitted a new drug application to China's National Medical Products Administration for ziresovir for treating RSV in infants aged 1 to 24 months, with the company expecting approval by 2026. If successfully launched, ziresovir could become the world's first approved specific anti-RSV therapeutic drug.

Regarding the selection of 1-24 month infants as the initial indication, Akeso stated that this population corresponds to more robust market demand and can bring significant commercialization opportunities in the short term.

However, Akeso also pointed out that clinical development of RSV pediatric therapeutic drugs presents significant challenges: pediatric drugs must follow a completely different and more stringent set of standards than adult drugs in terms of formulation, pharmacokinetics, toxicology, dosing, safety, clinical trial design, and regulatory pathways, requiring not only larger safety margins but also higher professional knowledge and technical capabilities. Additionally, antiviral drug development is inherently lengthy and resource-intensive, as viruses depend on human cellular mechanisms for replication, making it difficult to find selective drug targets with minimal side effects.

Previously, Akeso had withdrawn ziresovir's marketing application due to regulatory requirements for additional Phase III clinical trials in infants, and only resubmitted the marketing application in April this year after completing clinical trials.

On the other hand, while no RSV therapeutic drugs with the same target as ziresovir are currently marketed domestically, the current RSV market is dominated by prevention drugs, with the therapeutic drug market still in its early stages. Additionally, after prevention drugs are approved, the risk of RSV infection among susceptible populations will significantly decrease, meaning that even if ziresovir ultimately receives approval, its subsequent market development and commercialization process will still face certain challenges.

In this context, how Akeso will respond to competition and formulate commercialization strategies remains to be seen, as the company has not responded to media inquiries as of publication.

Currently, multinational companies including Pfizer, Gilead, and Johnson & Johnson are also advancing RSV therapeutic drug development globally. Among domestic pharmaceutical companies, ASC10 from Ascletis-B (01672.HK) and VV116 from Vigonvita are also conducting related RSV treatment research and development.

In the RSV vaccine field, which represents "active immunity," three products have been approved globally: Pfizer's Abrysvo, GSK's Arexvy, and Moderna's mResvia. The first two are recombinant protein subunit vaccines, while the last is an mRNA vaccine. The approved indication populations mainly focus on high-risk adult groups and adults over 60 years old.

In terms of performance, Abrysvo achieved sales of $755 million in 2024, while Arexvy recorded sales of £590 million (approximately $788 million) during the same period.

Domestic companies including Advaccine, AIM Vaccine (06660.HK), Chongqing Zhifei Biological Products Co.,Ltd. (300122.SZ), Sirnaomics-B (02257.HK), Walvax Biotechnology Co.,Ltd. (300142.SZ), and Changchun Bcht Biotechnology Co. (688276.SH) are all advancing RSV vaccine development.

According to professional sources, RSV active immunization vaccine development also faces significant challenges, requiring solutions to core difficulties including vaccine efficacy and immunogenicity. Taking immunogenicity as an example, infants have immature immune systems and possess maternal anti-RSV antibodies, while elderly individuals have weakened immune responses to vaccines due to reduced immunity. This makes it difficult to design universal RSV vaccine solutions suitable for all target populations, necessitating targeted development based on different population characteristics.

In fact, global infant RSV vaccine development has experienced over 60 years of challenges and has yet to achieve breakthrough results.

Overall, whether through active immunity, passive immunity, or antiviral drugs, all approaches have broadened pathways for commercialization in the RSV prevention and treatment field, creating more possibilities.

"The next growth inflection point in the global market will come from approval of infant/pediatric indications and inclusion in immunization programs. Infant vaccination demand is notably rigid, and approval of new vaccination populations will drive structural market growth. Additionally, beyond commercial markets, global public health procurement systems like Gavi will also become important sources of incremental growth. Since over 95% of RSV-related deaths occur in low- and middle-income countries, future improvements in vaccine accessibility through public procurement and aid programs will be one of the drivers of market growth," said Ban Wenli, Associate Director at Frost & Sullivan.