Nowadays, the pharmaceutical market is mainly divided into two tracks: small molecule chemical drugs and large molecule biopharmaceuticals, which have vastly different molecular structures, production processes, and patent protection logic. Small molecules use chemical synthesis pathways, while large molecules rely on biological cells for preparation. The differences in underlying technologies directly widen the gap in patent layout, competitive games, and cycle management between the two parties. This article deeply analyzes the patent layout logic of two types of drugs, providing professional references for industry innovation and commercial competition.

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1、 The Importance of Patent Layout for Small and Large Molecule Drugs

The inherent characteristics of high investment, high risk, and strong regulation in the pharmaceutical industry determine that patent layout is a core and necessary option for the full chain development of pharmaceutical companies. According to data from CCTV, the average development cost of a new drug exceeds 1 billion US dollars, with a development cycle of 10 to 15 years, and about 90% of candidate drugs fail in clinical trials. In this context, patent layout has become a key means for pharmaceutical companies to avoid risks and lock in innovative value.

（1） For pharmaceutical companies: patent layout is the core guarantee for R&D returns

During the patent exclusivity period, the gross profit margin of innovative drugs can generally reach over 80%; After generic drugs are launched, the price of the original drug usually drops by 50% to 70%, resulting in a significant reduction in profits. Taking Pfizer’s Vyndamax as an example, the company has extended the patent expiration date to 2035 through its crystalline patent layout, effectively avoiding the risk of “patent cliff” and ensuring stable revenue.

At the same time, patent portfolio is also a core chip for pharmaceutical companies to raise funds and authorize overseas expansion. As of April, the transaction heat of domestic innovative drug license out is unprecedented, with a total disclosed amount of 60.4 billion US dollars, accounting for more than 40% of the total amount in 2025. The high-quality patent portfolio directly determines the transaction value and enterprise valuation. Among them, small molecule drugs rely on compound and crystal form patents to construct structural barriers, while large molecule drugs rely on process and cell line patents to lock in production cores, forming differentiated competitive advantages.

（2） For the industry: Patent layout is the key to innovation incentives and order regulation

By 2025, the pharmaceutical industry will account for 4.3% of global PCT international patent applications. China ranks first in the world with 73718 PCT applications, and the continuous growth of patent applications in the pharmaceutical field is driving continuous breakthroughs in small molecule new chemical entities, large molecule new targets, and new processes. At the same time, the patent system clarifies the boundaries of innovation, which helps to curb malicious imitation. For example, the invalidation of Rosuvastatin’s crystalline patent and the early launch of generic drugs 9 years ago directly led to a significant reduction in the market share of the original drug, highlighting the importance of patent layout.

（3） For the market: balancing patent layout, innovation incentives, and accessible medication

Patent exclusivity incentivizes pharmaceutical companies to invest in the research and development of difficult to treat drugs, while the launch of generic drugs after patent expiration helps to reduce drug prices. For example, after Rosuvastatin entered the medical insurance, the price of the 50mg specification drug decreased from 166 yuan per pill to 95.5 yuan, significantly improving the accessibility of medication for patients. In addition, global patent layout is a necessary prerequisite for local pharmaceutical companies to go global. Hanqu You from Fosun Pharma has become the first monoclonal antibody biosimilar approved in China, Europe, and the United States through its comprehensive global patent layout, successfully achieving global commercialization.

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2、 Logic of patent layout for small molecule and large molecule drugs

2.1 Logic of Patent Layout for Small Molecule Drugs

The core advantages of small molecule drugs are clear structure, easy synthesis, and strong replicability. The logic of its patent layout can be summarized as follows: “using core compound patents as locks, peripheral patents as shields, layer by layer defense, extending the protection period”, constructing a three-dimensional protection network of “core patents+peripheral patents+defense patents”.

（1） Core Patent: Compound Patent

Compound patents are the most powerful type of patent for small molecule drugs, protecting the chemical structure of active pharmaceutical ingredients themselves and serving as the “anchor” for the entire patent layout.

Scope of Protection: Covering the general structure of compounds, specific preferred compounds, pharmaceutically acceptable salts, and stereoisomers. Regardless of the synthetic route or preparation process adopted by competitors, as long as the product contains a protected chemical structure, it constitutes infringement.

Layout timing: Following the principle of “first synthesis equals application”, patent applications should be submitted in the early stage of drug development (lead compound optimization stage) to seize the priority date.

Writing points: Adopt Markush claims, cover a series of similar compounds with general formulas, and expand the scope of protection; The instruction manual should fully disclose the preparation methods, activity data, and pharmacological validation results of representative compounds.

Protection period: The protection period for compound patents is usually 20 years, starting from the date of application and serving as the countdown to the drug’s lifecycle.

（2） Peripheral patents: multidimensional extension

Relying solely on core compound patents is difficult to achieve long-term protection. With the deepening of research and development, it is necessary to optimize the core structure, layout peripheral patents such as crystal form, salt form, formulation, use, and process, extend the protection period, and increase the difficulty of avoiding generic drugs.

① Crystal and salt type patents

The same compound can exist in multiple crystal forms (such as amorphous, crystal form A, crystal form B), and different crystal forms have significant differences in solubility, stability, bioavailability, and other aspects; Salt forms improve the drug properties of compounds by combining with acids and bases. The core means of extending the protection period. Data shows that 60% -80% of solid/semi-solid small molecule new drugs will have crystal form patents, and some drug crystal form patents can extend the protection period by more than 10 years. For example, the Sofpironium compound patent expires in 2026, and its crystal form patent is valid until 2040, with an additional 13.5 years of protection.

Defining crystal forms through various analytical methods such as XRPD, DSC, FTIR, etc., to avoid single methods being avoided; The claims are expressed as “including” rather than “composed of”, expanding the scope of protection.

② Formulation patent

The formulation design, prescription composition, and administration route of drugs protected by formulation patents include ordinary tablets, capsules, sustained-release formulations, targeted formulations, injections, etc. Developing differentiated formulations around the clinical needs of core compounds, such as converting short acting drugs into long-acting formulations, oral formulations into injectable formulations, and ordinary formulations into targeted formulations, not only enhances clinical competitiveness but also creates new patent barriers.

③ Application patent: Expanding indications

The new indications, combination therapy regimens, and dosages of compounds protected by utility patents are important means for small molecule drugs to tap into market potential and extend their lifecycle. On the basis of core indications, continue to conduct clinical research and expand new treatment areas (such as extending anti-tumor drugs to autoimmune diseases); Layout joint drug patents, protect combination schemes with other drugs, improve treatment efficacy, and increase the difficulty of avoiding generic drugs.

④ Process Patent: Protecting Synthetic Routes

The synthesis route, key intermediates, reaction conditions, purification methods, etc. of compounds protected by process patents, although the scope of protection is smaller than that of compound patents, can restrict generic drugs from the production end, especially suitable for forming new technological barriers through process optimization after the expiration of core patents.

Protect non obvious technological innovations such as key synthesis steps, highly selective catalysts, and efficient purification processes, and avoid patent instability caused by process standardization.

（3） Defense Patent

Defense patents refer to actively laying out technical solutions that competitors may avoid, pre positioning, and preventing competitors from bypassing core patents through simple structural modifications, dosage form modifications, and other means.

Design analogues and derivatives around the core compound structure, and apply for patents in advance; Layout alternative solution patents for peripheral technologies such as crystal forms, formulations, and processes, forming a “patent jungle” that allows generic drug companies to have no loopholes to exploit. The core characteristics of macromolecular drugs (represented by antibodies, fusion proteins, ADC drugs) are complex structures, dependence on live cell production, and deep binding between products and processes. Its patent layout cannot be fully protected by a single structural patent alone, and it needs to build a full chain technical barrier around “molecular structure, expression vector, host cell, production process, formulation, and use”.

2.2 Logic of Patent Layout for Large Molecule Drugs

（1） Basic Patent: Molecular Structure Patent

The basic patents for macromolecular drugs are amino acid sequence patents and structural patents, which protect the primary sequence, spatial structure, functional domains (such as the CDR region of antibodies) of the drug, and are the core foundation of the layout.The complex structure of macromolecules, especially protein drugs such as antibodies, may result in significant functional changes due to small sequence differences, making it difficult to cover all similar structures with a single patent; And global judicial practices, such as the Amgen v. Sanofi case, have become increasingly strict in restricting “functional gene patents”, requiring that “the wider the scope of protection, the more comprehensive the disclosure content,” significantly reducing the stability of broad structural patents. Apply for patents focusing on core functional areas such as antibody CDR regions and receptor binding domains; Adopting the writing method of “specific sequence+conservative variant”, moderately expanding the scope of protection; Reserve sufficient activity validation data to demonstrate the correlation between sequence and function, and improve the probability and stability of patent authorization.（2） Core Patent: Collaborative Layout of Process/Carrier and Platform Technologies

The characteristic of “product as process” for macromolecular drugs determines that process patents, carrier patents, and cell line patents are the most essential means of protection. At the same time, platform technology and specific point mutation patents can provide wider and more stable protection, and the two work together to build a more comprehensive patent barrier.

 

① Expression Vector and Host Cell Patent

Expression vectors are the “transportation vehicles” carrying genes, while host cells are the “factories” producing drugs, both of which have extremely high protective value. Patents can directly block competitors from using the same production system, forming a ‘production barrier’.

② Production process and platform technology patents

The production process covers gene cloning, cell culture, protein expression, purification, modification and other links, and any small changes may lead to differences in product quality. Since biosimilars require replication of the original research process to ensure product consistency, process patents can directly increase the threshold for imitation; Focusing on technology platforms such as CrossMab and structural modifications in CDR regions, layout platform patents and site mutation patents.

（3） Derivative patents: formulation, use, and combination patents, extending protection period

Similar to small molecules, large molecule drugs also need to lay out derivative patents to expand clinical value and prolong market exclusivity, but the focus of the layout is different.

① Formulation Patent: Focusing on Stability and Delivery Efficiency

Large molecule drugs (especially antibodies) have poor stability, easy degradation, and short half-life. Formulation patents focus on protecting stable prescriptions, long-acting formulations, targeted delivery systems (such as ADC drug linkers and toxins), etc., to enhance drug stability and clinical convenience.

② Usage and Combination Drug Patents: Expanding Clinical Scenarios

Develop new indications, combination therapy regimens, biomarkers, and other patents around core macromolecular drugs to expand the field of treatment; Especially in the field of cancer treatment, combination therapy has become mainstream, and related patents can significantly enhance the competitiveness of the drug market.

③ ADC drug special layout: components+combination patents

ADC drugs consist of three parts: antibodies, linkers, and payloads. The patent layout should take into account both individual component patents and combination patents.

Component patents: protect the structure and preparation process of antibodies, linkers, and toxins respectively; Combination patent: protects the combination method, connection site, drug ratio, etc. of the three, preventing opponents from evading the patent by replacing components; Risk Warning: Combination patents are easily restricted by component basic patents, and it is necessary to obtain component patent authorization in advance to avoid infringement risks.

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4、 Practical strategies for patent layout of pharmaceutical companies

Based on the logical differences in the layout of small molecule and large molecule drugs, pharmaceutical companies need to establish differentiated and implementable patent layout practice paths based on their own research and development strength and development stage, taking into account innovation protection and risk avoidance, and adapting to industry development trends and market competition needs.（1） Small molecule drug layout strategy

In response to the clear structure and ease of replication of small molecule drugs, pharmaceutical companies at different stages of development need to focus on core priorities, layer layout, and maximize patent value. Start up pharmaceutical companies have limited resources and should focus on the core breakthrough point of new chemical entities (NCEs). They should submit compound patent applications during the lead compound optimization stage, seize priority dates, and lock in core structure protection rights; Simultaneously layout crystal and salt patents, quickly establish preliminary patent barriers, and reduce early research and development risks.

Mature pharmaceutical companies need to rely on existing core compounds, comprehensively expand the dimensions of patent protection, layout patents around peripheral fields such as formulations, uses, production processes, and combination drugs, build a three-dimensional protection network, extend the patent protection period, and avoid the risk of “patent cliff”. In addition, for the core patents of original drugs, it is necessary to actively carry out technological innovations such as structural modification, crystal screening, and process optimization to achieve the dual goals of “avoiding infringement+independent innovation” and enhance core competitiveness through the combination of imitation and innovation.

（2） Layout strategy of macromolecular drugs

The characteristic of “product as process” for large molecule drugs determines that the core of their layout lies in the full chain technology protection, and different types of pharmaceutical companies need to accurately position the layout focus. Start up pharmaceutical companies should avoid the core target patent jungle and prioritize the layout of key technology patents such as expression vectors, host cells, and core production processes. They should focus on the research and development of large molecule drugs with new targets and mechanisms of action, create their own technological barriers, and reduce infringement risks and research and development costs.

Mature pharmaceutical companies need to establish a full chain patent layout of “components+combinations+processes+formulations”, especially for complex macromolecular drugs such as ADCs and bispecific antibodies. They should sign authorization agreements with component patent holders in advance to avoid infringement disputes; At the same time, continuously optimize production processes and formulation formulas, lay out related extended patents, and consolidate market advantages. Biosimilar drug companies need to focus on avoiding core patents of original drugs and independently developing exclusive expression vectors, host cells, and production processes. At the same time, they need to layout differentiated patents such as process optimization, quality control, and formulation improvement to form competitive differences with original drugs and enhance market competitiveness.

（3） General Strategy

Whether it is small molecule or large molecule drugs, local pharmaceutical companies need to follow three general strategies to enhance the scientific and effective patent layout.

Firstly, promote full lifecycle management of patents. Integrate patent layout throughout the preclinical, clinical, post marketing, and patent expiration stages of drugs, dynamically adjust layout strategies, and maximize patent value. According to statistics, pharmaceutical companies implementing full lifecycle patent management can increase patent conversion efficiency by over 40%.

Secondly, promote global patent layout. Simultaneously submitting patent applications in core pharmaceutical markets such as China, the United States, Europe, and Japan, building a global patent protection network, laying the foundation for the global commercialization of drugs, and avoiding failure to go global due to regional patent deficiencies.

Thirdly, adhere to the principle of prioritizing patent quality. Abandoning the layout misconception of “quantity over quality”, focusing on high-value and high stability patents, strengthening experimental data support, improving the probability of patent authorization and the stability of property rights confirmation, and laying a solid foundation of intellectual property rights for the long-term development of enterprises.

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5、 Conclusion

In the future, with the rapid development of AI drug research and development, synthetic biology, gene editing and other technologies, the patent layout of small molecule and large molecule drugs will face new opportunities and challenges: AI assisted structural design and process optimization will accelerate patent output, while also increasing the difficulty of patent creativity judgment; Synthetic biology will further enhance the “process as product” characteristic of macromolecular drugs, and the protection value of process patents will be further highlighted. Pharmaceutical companies need to keep up with technological development trends, continuously optimize patent layout strategies, and provide support for innovative drug research and development.

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