RAPT Therapeutics was originally founded as FLX Bio, with its original positioning being to regulate the migration and localization of immune cells in the tumor microenvironment through small molecules, and to influence the entry and exit of T cells and myeloid cells into the tumor by targeting the chemokine/chemokine receptors. This direction was considered scientifically very intelligent from 2014 to 2017, but later proved to be extremely difficult to commercialize.

On the one hand, the biggest problem with the chemokine system is its high redundancy, where one receptor typically binds to multiple ligands, and one ligand binds to multiple receptors, with each molecule having completely different effects in different tissues and disease stages. As a result, the inhibition of small molecules may not be thorough enough, or may be completely suppressed, leading to a sharp increase in the risk of side effects. The result is that in clinical practice, only slight clinical effects are often observed, but there is a lack of definite, clear, and meaningful therapeutic effects.

On the other hand, the core bottleneck of tumor immunity is not simply "inability to enter", but multiple factors such as T cell depletion, inhibitory myeloid cells, and matrix and metabolic barriers. Even if the distribution of immune cells is changed, it does not equate to tumor shrinkage. So although the mechanism of FLX Bio's small molecule project has certain scientific basis, it is difficult to change the clinical effect. In addition, the single drug effect is weak in clinical trials, the mechanism of combination therapy is unclear, biomarkers and patient stratification are difficult, ultimately leading to the difficulty of telling a clear and sustainable business story for its early Phase 1/2 data. Gradually, the progress of self-developed projects is slow, clinical signals are not strong enough, and stock prices have been hovering at low levels for a long time, causing investors to lose patience.

The real turning point for the company did not come from an original breakthrough within RAPT, but rather a very pragmatic and even slightly conservative strategic choice: to introduce (in license) an IgE antibody project.

RAPT Therapeutics actively and systematically abandoned the path of improving early pipelines through self iteration. After repeated verification of multiple small molecule immunization projects, a consensus gradually formed within the company that even if these assets continue to be optimized, it is difficult to achieve qualitative changes in mechanism clarity, therapeutic efficacy, and commercial attractiveness. Therefore, the management decisively cut losses, no longer investing resources in marginal improvements, but restructuring from a strategic level, shifting the focus from whether I can rescue this project to a strategy centered on in license.

Omalizumab is the first generation and currently the most mature anti IgE monoclonal antibody, co commercialized by Genentech/Novartis (partially marketed by Roche). It binds to free IgE, preventing IgE from binding to Fc ε RI receptors on the surface of mast cells and eosinophils, thereby reducing the cascade amplification of allergic reactions. In clinical practice, omalizumab has been widely used in diseases such as allergic asthma and chronic spontaneous urticaria, thus verifying the core value of IgE targets in allergic diseases. The product will sell 3.7 billion US dollars in 2023.

However, as a first generation product, Oma has obvious limitations: it usually requires injection every 2-4 weeks, and the dosage is related to body weight and IgE levels. Medication burden and compliance remain pain points.

Three very practical questions raised by RAPT's search for IgE:

1. Can IgE be suppressed more deeply?
2. Can the inhibitory effect last longer?
3. Can the frequency of medication be extended from "once a few weeks" to "truly chronic disease level"?

In the Phase II clinical stage of Jeminchare/Shanghai Jiyu JYB1904 (the Chinese original research code for ozureprupart), this in licensed antibody showed:

Potential for sustained IgE suppression
There is a chance to achieve 8-12 week or even longer dosing intervals
Clearly distinguish from the 'first generation IgE experience'

RAPT recognizes the differentiated clinical value of JYB1904: deeper and more persistent IgE inhibition, as well as the potential to extend the dosing frequency from a few weeks to a truly chronic disease level experience. Instead of spending years rebuilding molecules from scratch, RAPT chooses to quickly exchange limited resources for the certainty of human data. RAPT has introduced JYB1904 assets with a down payment of $35 million and a milestone of around $672.5 million. On December 23, 2024, it signed an exclusive foreign license agreement with Jiyu Pharmaceutical for JYB1904, and obtained the development and commercialization rights in areas other than Chinese Mainland, Hong Kong, Macao and Taiwan.

After authorization from Jiyu Pharmaceutical, RAPT made ozureprubar a key pipeline for the company, while abandoning the promotion of other pipelines. In the next 13 months, ozureprubart will obtain positive data in phase IIb clinical trials for chronic spontaneous urticaria (CSU), demonstrating that the 12 week dosing regimen is equally effective and superior to the first generation IgE antibodies on the market compared to the 8-week regimen.

In recent years, GSK has clearly focused on the respiratory system, immunity and inflammation, and allergic diseases. RAPT's assets are precisely positioned in this strategic direction.

For large pharmaceutical companies, the ideal acquisition targets are:

Low target risk.
Appropriate clinical stage.
Clear commercial space.

From a time window perspective, the ozureprubar of RAPT obtained positive data in phase II clinical trials of chronic spontaneous urticaria (CSU), demonstrating that the 12 week dosing regimen is equally effective and superior to the first generation IgE antibodies on the market compared to the 8-week regimen. The key is that it has not yet entered phase III clinical research.

GSK is looking for similar products with the capability to complete Phase III and subsequent commercialization. Buying products that are much cheaper now than those that have completed Phase III clinical trials.

Clinically validated targets combined with phase II clinical data are the favorite assets of large pharmaceutical companies.

IgE antibodies are core assets that can be extended to various allergic diseases. That's why GSK acquired RAPT instead of just in license IgE antibodies. Directly buying out to avoid subsequent commercial disputes.

RAPT did not invent IgE antibodies, but they demonstrated the clinical value of next-generation IgE antibodies to major pharmaceutical companies.

In the transaction chain of Jiyu Pharmaceutical RAPT Therapeutics GSK, the IgE antibody product ozureprupart is more like a little girl: she was born in Jiyu Pharmaceutical, with natural beauty and distinct talents, and has not yet been truly recognized by the industry; RAPT took her hand and trained her to undergo international standard testing - advance consultation with regulatory agencies on approval pathways, global clinical design, effective communication with KOLs and international authoritative organizations, allowing her to learn to stand up, perform, be understood, and tested on the international stage; When Jiyu Pharmaceutical and RAPT outlined a clear outline for her, GSK no longer saw just a smart child, but a future protagonist with the ability to survive and expand globally - therefore, this was not a simple product transfer, but a life trajectory that had completed critical growth and was about to step onto the world stage.

Multinational pharmaceutical companies are systematically laying out innovation in China. The successful acquisition of RAPT demonstrates the acquisition logic of multinational pharmaceutical companies: Chinese companies have advantages in speed, efficiency, and cost. Overseas medium-sized biotech companies, with localized systems, standards, and narratives, have become true value enhancers and risk takers. And multinational pharmaceutical companies, with their vast global platforms, regulatory channels, and commercial networks, allow a molecule that was once born in a laboratory to truly go global, enter the market, and unleash its maximum medical and commercial value.