When developing a new therapy, the spotlight almost always falls on the molecule, antibody, or cell that drives the therapeutic effect – but the final product is more than just the active ingredient, it requires excipients to improve the qualities that make a therapy more druglike. Excipients determine whether an API remains stable, can be absorbed, tolerated, and protected from the immune system, and ultimately whether it works as intended in the body. Excipients are not accessories; they are essential.
In fact, in many marketed drugs, the concentration of inactive ingredients is 100 times greater than that of the active drug itself – yet, surveys consistently show that even many prescribing physicians do not distinguish actives from inactives when choosing formulations, nor do most appreciate how profoundly excipients influence effectiveness and side effects. Patients experience this disconnect daily when two generic versions of the “same” drug behave very differently in terms of tolerance or efficacy.
This knowledge gap is magnified in the new frontier of biologics. Biologics have transformed medicine, from the first therapeutic peptide (insulin for type 1 diabetes) to today’s booming pipeline of antibodies and peptides for cancer, autoimmune disorders, and metabolic disease. These therapies represent some of the most powerful drugs ever developed, but they are fragile. Assuming a biologic will find its target, persist there, and function optimally on its own is wishful thinking. Most antibodies directed at cancer are injected “naked” with excipients designed only for stability in the vial, not for functionality inside the body. That means efficacy is often compromised in ways that don’t show up until phase II clinical trials, where the cost of asset failure can exceed $1 billion.
From survive to thrive
The field is starting to ask how we can help fragile therapies thrive inside the body. One leading approach is building excipient systems from polymers already familiar to the FDA. These multifunctional systems can do more than stabilize in the bottle. Polymers can be designed to hold a therapy or API in a desired location and release it slowly over days or weeks, which can also help avoid first-pass loss in the liver or lungs. They can protect against immune attack, lower the dose required to achieve efficacy, and simplify storage and shipping, extending shelf life and reducing cost.
By their nature, these excipient systems have tunable polymer chemistry, which can be designed through a combination of chemistry and AI-driven predictive modeling to match the unique biology of each therapeutic product. For example, a retrieval-augmented generation (RAG)-based AI pipeline can be used to mine terabytes from historical data to recommend polymer backbones and crosslinking the chemistries most likely to succeed. This reduces wet-lab iterations, shortens timelines, and cuts costs.
Patients are directly impacted by excipients, even if they rarely think about them. In some cases, this may mean fewer injections or infusions thanks to extended-release formulations. Polymers with targeting capabilities can lead to more durable responses, reduced relapse risk, and fewer systemic side effects.
However, every innovation at the excipient level, whether reducing cost or expanding access, has ripple effects that eventually impact patients. Controlled release polymers can:
Increase drug-target residence time to unlock lower dosing
Simplify storage and logistics
Limit degradation from temperature fluctuations.
Practically, this means therapies that would otherwise require specialized processes and facilities to maintain ultralow temperatures can instead be shipped on dry ice or ambient temperatures and stored in community clinics. These are not incremental improvements but step-changes in how therapies reach the patients that determine whether groundbreaking biologics succeed in the real world.
The next decade will mark a shift in how biotech thinks about drug design. Success will no longer be defined by discovering a potent molecule, but by ensuring it reaches the patient in a safe, stable, and effective form. Inactive ingredients, long treated as afterthoughts, will become the central drivers of innovation that can improve human health by making excipients a foundation, not a footnote, of biotech development.
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