Selecting drug delivery routes is one of the earliest decisions that can shape a drug development program. The route affects formulation strategy, exposure, patient use, analytical testing, device needs, manufacturing controls, and the path to IND-enabling studies.

For biotech and pharma R&D teams, the right route is rarely based on convenience alone. It must match the molecule, indication, target tissue, dose, stability profile, and intended clinical use. A route that works for one asset can fail for another with similar therapeutic intent.

That is why drug delivery route selection should start early. It gives formulation scientists, CMC teams, and development leaders a clearer path from feasibility work to preclinical testing, clinical supply planning, and tech transfer.

Why Drug Delivery Route Selection Shapes the Entire Development Program

Choosing a drug delivery route affects more than how a patient receives the drug. It changes the formulation requirements, analytical methods, excipient strategy, packaging, device considerations, and release testing plan.

An oral tablet, sterile injectable, nasal spray, ophthalmic suspension, pulmonary product, and transdermal patch each create different development demands. Each route also carries different risks related to absorption, local tolerance, dose uniformity, stability, and manufacturability.

Early route selection helps teams decide which questions to answer first. Should the program focus on solubility enhancement, sterile processing, permeability, particle size control, preservative compatibility, aerosol performance, or skin penetration? The answer depends on the route and the molecule.

How Route Choice Determines Pharmacokinetic and Patient Outcomes

Route choice strongly affects pharmacokinetics. Oral drug delivery may expose the drug to gastric pH, enzymes, intestinal transporters, and first-pass metabolism. Parenteral drug delivery can bypass the gastrointestinal tract and support systemic exposure, but it may require sterile processing, controlled tonicity, and careful management of injection-site tolerability.

Pulmonary drug delivery can support local lung exposure or rapid systemic absorption, but it depends on aerosol performance, particle size, inhalation pattern, and device compatibility. Nasal drug delivery may offer rapid absorption and avoid first-pass metabolism, but nasal residence time, mucociliary clearance, and local tolerability can limit performance.

Ophthalmic drug delivery must account for tear turnover, corneal barriers, drug retention, comfort, and local tissue exposure. Transdermal drug delivery must address skin permeability, dose limitations, adhesive performance, and irritation risk.

Patient outcomes depend on the same variables. A route that improves exposure but creates difficult administration may hurt adherence. A route that appears simple may fail if it requires frequent dosing or causes local discomfort.

Why Switching Routes Mid-Program Is Costly and Avoidable

Switching routes after early development often forces teams to repeat major work. A change from oral to injectable delivery, for example, can require new formulation development, new analytical methods, new excipient evaluations, new stability studies, and new toxicology material.

Route changes can also affect nonclinical study design. The selected route should match the intended clinical route whenever possible. When it does not, teams need a scientific reason for the difference and a plan for bridging exposure, safety, and formulation performance.

Mid-program route changes also affect timelines. Teams may need to source new packaging, assess device options, change manufacturing processes, and update CMC documentation. These issues can delay IND preparation and increase spend.

Many route changes are avoidable when teams test route feasibility early. A structured formulation screen, paired with analytical method development services, can reveal whether the chosen route has a reasonable path forward before the program commits too much time and budget.

How Molecule Properties Constrain the Delivery Route Decision

The molecule should guide the route decision. Therapeutic goals matter, but the molecule sets the limits.

A small molecule with acceptable solubility, permeability, and stability may support oral delivery. A poorly soluble compound with high potency may need a lipid-based formulation, nanosuspension, amorphous solid dispersion, or another formulation approach. A peptide may need protection from enzymatic degradation. A biologic may need parenteral delivery because of size, structure, and stability concerns.

Early drug delivery formulation work should define what the molecule can tolerate, where it can dissolve, how it degrades, and what dose the intended route can support.

Solubility, Permeability, and the BCS Framework

For many small molecules, BCS classification formulation work helps teams understand oral feasibility. The Biopharmaceutics Classification System considers solubility and intestinal permeability. It can help teams identify whether absorption is more likely limited by dissolution, permeability, or both.

A high-solubility, high-permeability compound may have a clearer oral path. A low-solubility compound may need solubility enhancement before oral drug delivery can work. A low-permeability compound may need a different strategy because improving solubility alone may not solve absorption.

BCS classification formulation work does not answer every question. Food effects, metabolism, transporters, dose, particle size, and solid-state form can still affect performance. But BCS thinking gives R&D teams a useful starting point for choosing a drug delivery route.

For non-oral routes, solubility and permeability still matter. Injectable formulations need appropriate solubility at the target dose and acceptable pH, osmolality, viscosity, and excipient levels. Ophthalmic and nasal products need enough solubility and retention to support local exposure. Transdermal systems need sufficient potency and skin permeation.

Stability Across Physiological, Storage, and Manufacturing Conditions

A route may look attractive until the molecule meets real conditions. Physiological pH, enzymes, temperature, light, oxygen, shear, agitation, and sterilization can all change stability.

Oral products must survive gastric and intestinal conditions long enough to reach the absorption site. Nasal and pulmonary products face local enzymes, mucus, and clearance. Ophthalmic products must remain stable in a sensitive environment with tight limits on irritation. Parenteral products must remain stable in sterile systems and may need compatibility with syringes, vials, stoppers, and infusion materials.

Storage conditions matter as much as in-use conditions. A formulation that works during a short screen may fail during longer stability testing. Teams need early data on chemical degradation, aggregation, precipitation, pH shift, preservative loss, and container closure compatibility.

Manufacturing can also create stress. Mixing, filtration, milling, lyophilization, terminal sterilization, aseptic fill, spray drying, and device filling may expose the molecule to conditions that change its performance. Route selection should account for these stresses early.

Why Biologics, Peptides, and Small Molecules Require Different Decision Logic

Small molecules often give teams more route options, but they can still be constrained by solubility, permeability, metabolism, and dose. A compound that appears orally suitable may need a complex formulation to reach exposure targets.

Peptides often face enzymatic degradation and poor permeability, especially through the gastrointestinal tract. Some peptide programs explore oral, nasal, transdermal, or pulmonary approaches, but these routes require careful evidence. The formulation must protect the molecule and support absorption without creating unacceptable safety or tolerability issues.

Biologics usually require different logic. Proteins, antibodies, and other biologics can be sensitive to pH, temperature, interfaces, agitation, and concentration. Biologics formulation route decisions often involve parenteral formats, including intravenous, subcutaneous, or intramuscular delivery.

High-concentration biologics may create viscosity and syringeability challenges. Subcutaneous delivery may improve convenience, but dose volume and stability can limit feasibility. Intravenous delivery may support larger doses, but it creates different clinical and commercial considerations.

How Therapeutic Goal and Target Tissue Narrow the Route Options

The therapeutic goal can quickly narrow the route options. A systemic therapy may need reliable plasma exposure. Local therapy may need high drug concentration at the target tissue with limited systemic exposure.

For a gastrointestinal target, oral delivery may make sense if the drug can reach the local site and remain active. For an ocular target, ophthalmic drug delivery may be preferred when the formulation can overcome tear turnover, corneal barriers, and short residence time. For lung diseases, pulmonary drug delivery may place drugs near the target tissue, but aerosol properties and device performance become central.

For central nervous system programs, nasal delivery may be considered in specific cases, but teams need strong evidence for absorption and distribution. For dermatology, transdermal or topical delivery may support local effects, but skin barrier function can limit drug entry.

Target tissue also affects safety. Local delivery may reduce systemic exposure, but it can increase local tolerability demands. Systemic delivery may improve distribution, but it can create broader safety questions.

The key question is direct: Where does the drug need to be, at what concentration, for how long, and with what level of patient burden?

How Patient and Commercial Factors Influence Final Route Selection

The molecule and biology define what is possible. Patient and commercial factors help determine what is practical.

A route that works scientifically may still fail if it does not fit real clinical use. Frequent injections may reduce adherence. A large tablet may be hard to swallow. A nasal spray may not be ideal if local irritation limits repeated use. An ophthalmic product may need a dosing schedule patients can follow.

Patient population matters. Pediatric, geriatric, inpatient, outpatient, and self-administered products each create different requirements. A route that works in a controlled clinical setting may be less practical for chronic home use.

Commercial factors also matter. Teams should consider dose frequency, device needs, cold chain, cost of goods, packaging, line availability, and tech transfer. These factors should not override scientific feasibility, but they should enter the route decision before the program locks into a path.

For many sponsors, the best route balances exposure, safety, usability, manufacturing feasibility, and clinical differentiation. That balance is easier to find before formulation work becomes too narrow.

When the Obvious Route Is the Wrong Route

The obvious route is often based on habit. Small molecules are expected to be oral. Biologics are expected to be injectable. Local diseases are expected to use local delivery.

Those assumptions can be useful, but they can also hide risk. Drug development services should test assumptions early, especially when the molecule has unusual solubility, stability, dose, permeability, or target tissue needs.

A formulation development CRO can help R&D teams separate route preference from route feasibility. That distinction matters when timelines are tight and the program needs a defensible path into IND-enabling work.

Poorly Soluble Small Molecules That Look Oral on Paper

Many small molecules begin with an oral target product profile. That may be reasonable, but poor solubility can make oral exposure difficult.

A compound may show potency in vitro and acceptable early pharmacology, yet fail to reach sufficient exposure after oral dosing. The problem may involve low dissolution, precipitation in the gut, poor permeability, high first-pass metabolism, or food effect risk.

In these cases, oral delivery may still be possible, but it may require focused formulation work. Teams may need particle size reduction, salt screening, lipid-based systems, solid dispersion, pH adjustment, surfactants, or other approaches.

Sometimes the better decision is to test another route early. Parenteral drug delivery may be appropriate for certain compounds, especially when oral exposure remains poor and the therapeutic context supports injection. The route decision should follow data, not the initial assumption.

Biologics That Cannot Survive Their Intended Route

Biologics can fail when the intended route exposes them to conditions they cannot tolerate. Oral biologics face degradation and poor permeability. Nasal and pulmonary biologics may face stability, absorption, immunogenicity, and device-related questions. Subcutaneous biologics may face concentration, viscosity, aggregation, and injection volume constraints.

For biologics formulation route work, teams need early studies that assess aggregation, degradation, potency, excipient compatibility, and container-closure interaction. Route selection should also account for administration frequency, dose, and patient setting.

A biologic intended for self-injection may need high concentration and low viscosity. That can be difficult for some proteins. An intravenous route may reduce concentration pressure, but it can increase clinical burden.

The wrong route can create a formulation problem that no amount of late work can fully solve. Early route assessment reduces that risk.

How Drug Delivery Route Selection Fits the IND-Enabling Timeline

Route selection should begin before IND-enabling studies are locked. At that point, teams need a formulation that can support toxicology studies, analytical testing, stability work, and early clinical planning.

Preformulation studies can assess solubility, pH stability, solid-state properties, excipient compatibility, degradation pathways, and preliminary manufacturability. These data help teams decide whether a route has enough support to move forward.

The IND-enabling timeline also requires alignment between formulation, analytical, and nonclinical plans. If the toxicology formulation differs from the planned clinical formulation, teams need to understand why and how the data will be used.

Analytical methods should be fit for purpose at each stage. Early methods may focus on assay, impurities, degradation, concentration, particle size, viscosity, osmolality, or release rate, depending on the dosage form. As the program advances, methods may need refinement for stability, release, and comparability.

A pharmaceutical contract research organization with formulation and analytical capabilities can help connect these pieces. The goal is to avoid fragmented decisions where formulation, toxicology, analytical testing, and CMC planning move in different directions.

How a Formulation CRO Approaches Route Selection With R&D Teams

A formulation CRO approaches route selection by combining molecule data, therapeutic goals, route feasibility, and development constraints.

The process often starts with a review of the target product profile, known molecule properties, dose range, indication, target tissue, prior formulation work, and available pharmacokinetic data. From there, the team identifies route options and the key risks for each one.

For a poorly soluble small molecule, the route assessment may focus on solubility, dissolution, permeability, and exposure risk. For a biologic, it may focus on stability, concentration, aggregation, viscosity, and administration volume. For an ophthalmic, nasal, pulmonary, or transdermal product, it may focus on local barriers, retention, tolerability, and device fit.

CRO facilities and capabilities also matter. Route selection is stronger when the partner can run formulation screens, analytical testing, stability studies, and early manufacturability assessments in a connected way.

A good CRO partner should help R&D teams answer practical questions:

• Can the intended route support the required dose?
• Can the molecule remain stable through storage and use?
• Can the formulation be tested with reliable methods?
• Can the dosage form be made with a realistic process?
• Can the selected route support the preclinical and clinical plan?
• Can the route support future tech transfer?

Integral BioSystems supports formulation, drug delivery, analytical method development services, and related contract research organization services for complex development programs. That combination helps sponsors evaluate route options with both scientific and CMC needs in view.

Need Help Selecting Drug Delivery Routes for Your Molecule?

Selecting drug delivery routes is easier when route feasibility, formulation behavior, analytical testing, and development timing are reviewed together. Early route decisions can reduce rework, improve study planning, and give R&D teams a clearer path toward IND-enabling work.

Integral BioSystems works with biotech and pharma teams that need formulation and drug delivery support for small molecules, peptides, biologics, ophthalmic products, injectables, nasal products, pulmonary products, and other complex dosage forms.

To discuss your molecule, contact Integral BioSystems. Our team can help assess route options, identify formulation risks, and plan the studies needed to support your next development decision.The Problem: UV Exposure and Ocular Tissue Damage

Ultraviolet radiation is absorbed by multiple structures of the eye and is correlated with a range of ocular disorders, including corneal pterygia, cataracts, keratoconus, glaucoma, choroidal neovascularization (CNV), and age-related macular degeneration (AMD). UVR is categorized into three bands: UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm).

The cornea absorbs more than 90% of UVB and approximately 60% of UVA, while the retina absorbs UVA and blue light in the 300–800 nm range. At the cellular level, UVA and UVB cause damage to DNA through the production of reactive oxygen species (ROS), which trigger tissue-damaging inflammatory cytokines. The cumulative effect of this oxidative stress contributes to the progression of multiple ocular conditions over time.

Despite the well-established link between UV exposure and ocular disease, there is no widely adopted topical ophthalmic product that combines UV-blocking properties with antioxidant and anti-inflammatory activity in a single formulation designed for sustained ocular surface residence.

OcuHeal-UV400+: A Lipid Nanoparticle Eye Drop with UV-Blocking and Antioxidant Properties

Integral BioSystems developed OcuHeal-UV400+, a lipid nanoparticulate (LNP) eye drop formulated using its proprietary OcuHeal LNP technology platform. The product contains IB0108, a GRAS-designated antioxidant compound with decades of safe use as an oral supplement in humans and animals.

Key attributes of IB0108 and the OcuHeal-UV400+ formulation include:

• IB0108 is an FDA GRAS compound approved for daily oral consumption as a dietary supplement.
• It functions as an ROS quencher and antioxidant with anti-inflammatory, immunoprotective, and UV-protective properties.
• IB0108 blocks portions of UVA and UVB radiation in a dose-responsive manner.
• When encapsulated in the OcuHeal™ LNP platform, the entire UV wavelength range from 200 to 600 nm is blocked, extending coverage across UVA, UVB, and UVC.
• The OcuHeal™ LNP platform uses lipid nanocores with a particle size under 200 nm, enabling penetration of the ocular mucosal meshwork pores (approximately 500 nm).
• OcuHeal™ patents have been granted in 14 global jurisdictions.

A stabilized form of IB0108 was also developed, enabling short-term storage at 25°C/60% relative humidity. Stability recovery data showed greater than 88% recovery at 1 week and greater than 92% recovery at 12 weeks for the stabilized formulation, compared to lower recovery rates for the original form of the molecule.

Research Design and Methods

The research, presented at the 2025 ARVO Annual Meeting (Poster 4341 – A0497), characterized OcuHeal-UV400+ across UV-blocking efficacy, corneal cell protection, pharmacokinetic distribution in ocular tissues, and in vivo safety and tolerability.

OcuHeal-UV400+ was prepared as a nano-dispersion using a proprietary process. IB0108 content was measured by HPLC (Shimadzu Prominence). Particle size distribution was determined by laser diffraction (Horiba 950V2). UV-blocking properties were measured by UV-Vis spectrometry (Shimadzu). IB0108 incubation studies with human corneal epithelial cells (HCEC) in the presence of UVB (254 nm) were performed at the University of Waterloo. Bioanalytical analysis of ocular tissues was performed by LC/MS/MS using a validated method across cornea, iris/ciliary body, lens, retina, optic nerve, conjunctiva, sclera, eyelids, tear fluid, aqueous humor, and vitreous humor. Blood was analyzed for systemic exposure. Safety and tolerability were assessed in New Zealand White Rabbits using the SPOTS scoring system (Eaton et al. 2017) at 1, 2, 4, and 6 hours post-dosing.

Key Findings from the Research

The following results are relevant for teams evaluating ophthalmic formulation development strategies for UV-protective or antioxidant ophthalmic products:

UV-blocking efficacy:

IB0108 demonstrated dose-responsive UV-blocking behavior, with lower percent transmittance (higher UV blocking) at increasing concentrations. When encapsulated in the OcuHeal™ LNP, the formulation blocked the entire UV wavelength range from 200 to 600 nm, covering UVA, UVB, and UVC. This represents a significant enhancement over the UV-blocking characteristics of IB0108 alone.

Protection of human corneal epithelial cells:

In studies conducted at the University of Waterloo, IB0108 demonstrated a protective effect on human corneal epithelial cells (HCEC) exposed to UVB radiation at 254 nm. Cell viability data showed that IB0108 reduced UV-induced damage in a concentration-dependent manner, supporting the compound’s potential as a corneal cytoprotective agent.

Pharmacokinetic distribution across ocular tissues:

Following a single 80 mcg dose of IB0108 in OcuHeal eye drops administered to New Zealand White Rabbits, recovered concentrations of IB0108 were detected across multiple ocular tissues at 1, 2, 4, and 6 hours post-dosing. Tissues analyzed included the cornea, iris/ciliary body, lens, retina, optic nerve, and conjunctiva. Higher concentrations were observed in the conjunctiva, sclera, tear fluid, and eyelids, consistent with topical ocular delivery. The data demonstrate enhanced residence time on the ocular surface, with measurable IB0108 concentrations persisting through the 6-hour timepoint.

In vivo safety and tolerability:

OcuHeal-UV400+ lipid nanoparticles were assessed for signs of non-biocompatibility on the ocular surface at all timepoints, including IOP testing, redness, eyelid swelling, discharge, hyperemia, and corneal opacity, using the SPOTS scoring system. All scores were zero at all timepoints, indicating no adverse effects on any evaluated ocular parameter.

Formulation stability:

A novel stabilized form of IB0108 enabled short-term storage at 25°C/60% RH. The stabilized formulation maintained greater than 92% recovery at 12 weeks, compared to approximately 52.6% for the original form under the same conditions. This stability profile supports the feasibility of room-temperature storage and practical shelf-life requirements for a commercial ophthalmic product.

What This Means for Ophthalmic Development Teams

For R&D and product development teams working on UV-protective, antioxidant, or anti-inflammatory ophthalmic compounds, this research highlights several practical considerations:

• Encapsulation of a GRAS antioxidant in an LNP platform extended UV-blocking coverage from partial UVA/UVB to the full 200–600 nm range, covering UVA, UVB, and UVC.
• The OcuHeal™ LNP eye drop demonstrated a 6-hour ocular surface residence time with distribution across multiple ocular tissues, including posterior segment structures such as the retina and optic nerve.
• Zero adverse effects were observed across all SPOTS scoring parameters at all timepoints in preclinical testing.
• The stabilized formulation supports room-temperature storage, an important consideration for commercial viability and patient convenience.
• The product can function as a standalone UV-protective antioxidant eye drop or serve as a platform for formulating additional ophthalmic actives within the OcuHeal™ LNP system.

Integral BioSystems’ expertise in LNP-based ophthalmic delivery, combined with the OcuHeal™ platform, positions the company to support drug development services for UV-protective, antioxidant, and anti-inflammatory ophthalmic programs from feasibility through process engineering.

Read the Full Research

This blog post summarizes key findings from the ARVO 2025 poster by Barman K, Harris, Coleman, Belen, Ward, and Barman SP (Poster 4341 – A0497). To review the complete research, including UV-Vis spectrometry data, HCEC protection results, pharmacokinetic tissue distribution, tolerability scores, and stability data, download the full poster (PDF).

Explore all Integral BioSystems research on the publications page.

Discuss Your Ophthalmic Development Program

Whether you are evaluating LNP-based delivery for an ophthalmic antioxidant, exploring UV-protective formulations, or considering the OcuHeal™ platform for your compound, Integral BioSystems can support your program from feasibility through process engineering. Request a formulation consult to discuss your molecule and delivery objectives.