Core Takeaways

An in-situ forming gel is a delivery system that spontaneously forms a gel network at the administration site.

Phase transition is triggered by temperature, pH, ionic cues, or enzymatic reactions.

This "shape-shifting drug" extends duration, lowers dosing frequency, raises local concentration, and reduces systemic side effects.

In recent years, in-situ gels have made breakthroughs in ophthalmology, dermatology, and intratumoral injection, with a market CAGR above 15%.

1. In-Situ Gels: From Static Carriers to Smart Delivery

(1) Definition

An in-situ gel is a liquid dosage form that automatically converts to a gel under physiological conditions (body temperature, pH, ionic environment) after administration.

Compared with conventional gels, it offers clear advantages.

Conventional gels: pre-formed and already solid before use, with limited applications.

In-situ gels: administered as liquid and gel at the target site, offering easy use and high compliance.

(2) Four Triggering Mechanisms

Thermo-responsive: the most common type.

It uses polymers that dissolve at low temperature and solidify at body temperature; representative materials include Poloxamer 407 and PEG-PLGA copolymers.

pH-responsive: remains liquid under acidic conditions and gels under neutral or alkaline conditions.

Carbopol-based systems are typical; suitable for oral or injectable delivery.

Ion-triggered: gelation is driven by cations such as Ca²⁺ and Na⁺ in body fluids.

A typical system is sodium alginate crosslinked with Ca²⁺.

Enzyme-triggered: leverages matrix metalloproteinases (MMPs) highly expressed in the tumor microenvironment for enzymatic degradation and site-specific release.

2. Five Application Areas

(1) Ophthalmic Delivery, Solving the Compliance Challenge

Traditional eye drops for glaucoma and dry eye require frequent dosing, leading to poor compliance.

In-situ gel eye drops effectively address this industry pain point.

Dosing frequency drops from four times daily to once or twice.

Corneal residence time extends, raising bioavailability.

Systemic absorption is reduced, lowering toxic side effects.

(2) Subcutaneous/Intramuscular Injection: A Long-Acting Platform

In-situ gels serve as injectable sustained-release carriers, enabling release from weeks to months.

Peptide drugs (insulin, GLP-1 analogs): greatly reduce injection frequency.

Protein drugs (antibodies, enzymes): improve stability and extend half-life.

Hormonal drugs (leuprolide, goserelin): used in prostate and breast cancer treatment.

(3) Intratumoral Delivery for Precision Targeting

In-situ gels offer multiple unique advantages for intratumoral delivery and are an excellent vehicle for precision oncology.

Local high concentration: in-situ gelation with slow release maintains high local drug levels for days to weeks.

Reduced systemic toxicity: less drug enters blood, avoiding myelosuppression, cardiotoxicity, and other systemic side effects.

Injectability: minimally invasive fine-needle injection covers deep tumors and post-surgical cavity delivery.

Combination therapy: can co-deliver chemotherapeutics and immune checkpoint inhibitors for combination oncology treatment.

(4) Dermal Topical Delivery: An Innovative Transdermal Approach

Scar treatment: 5-FU in-situ gel for intralesional injection.

Skin cancer: bleomycin in-situ gel for local skin cancer treatment.

Acne: retinoid-based in-situ gels, improving stability and reducing irritation.

(5) Nasal Delivery: A New Route Across the Blood-Brain Barrier

In-situ gels enable nose-to-brain delivery via the nasal route, breaking through traditional limits.

Peptide drugs (insulin, octreotide): delivered to the brain via the nose-to-brain pathway.

Small molecules (midazolam): enable rapid nasal delivery for acute epileptic seizures.

Vaccines: suitable for intranasal mucosal vaccines against influenza, COVID-19, and others.

3. Technical Challenges: Core Hurdles to Industrialization

(1) Difficulty Precisely Controlling Gelation Time

Gelation speed directly affects administration; too fast causes clogging and injection difficulty.

Too slow leads to premature leakage and drug loss.

Gelation kinetics must be precisely optimized for each administration route.

(2) Insufficient Long-Term Stability of Loaded Drug

Some drugs encapsulated in the gel network undergo activity loss and degradation.

This is particularly acute for protein and peptide biologics in both storage and in vivo.

(3) Drug Burst Release

A burst release of large amounts of drug often occurs at the initial gelation stage.

This causes sharp fluctuations in plasma concentration, affecting safety and efficacy continuity.

(4) Difficulty Scaling Up Industrial Production

Lab-scale process parameters are hard to translate directly into commercial-scale production.

Sterility and batch uniformity are key hurdles, and consistent commercial-scale quality is hard to guarantee.

(5) High Raw Material Costs

High-end functional polymers such as Poloxamer 407 are expensive to source.

This drives up formulation costs and limits pricing and market competitiveness.

4. Market Landscape: A High-Growth Golden Track

(1) Global Market Size and Growth

According to Grand View Research, the global in-situ gel market reached about USD 3.8 billion in 2025.

It is projected to exceed USD 7.5 billion by 2030 at a CAGR of about 14.6%, maintaining rapid growth.

(3) Core Opportunities in China

Ophthalmic in-situ gels: a large glaucoma and dry-eye patient base offers broad import-substitution potential.

Intratumoral delivery: rising cancer incidence fuels strong demand for precision oncology.

High-end formulation CDMO: few Chinese firms have commercial-scale in-situ gel capacity, offering differentiation.

Improved new drugs: Category 2.2 long-acting in-situ gels are encouraged by policy, with shorter review timelines and faster launch.

5. Closing: A Small Track with Large Growth Potential

In-situ gels look like a mature improved-delivery technology, but new indications, dosage forms, and combination regimens continue to widen its innovation space.

With the advance of precision medicine and improved-drug policy, in-situ gels as a core delivery-enabling technology are rising in industry standing.

For CDMOs with formulation expertise, this track offers strong growth and long-term value.