Oakwood has over 20 years of experience developing sustained-release injectable pharmaceutical products, including small molecules (both hydrophilic and hydrophobic), peptides, and proteins. We use a variety of polymers with proven safety profiles to develop formulations with in vivo durations of two weeks to one year. We work with clients to determine the optimal target product characteristics in terms of:

• Active pharmaceutical ingredient (API)
• Selection of polymer
• Appropriate solvent system
• Duration of release
• Steady state levels
• Route of administration
• Drug load
• Particle size
• Vial size
• Needle size

---

Initiate a Feasibility Study

The feasibility study is a quick way to determine if the target product profile is achievable with our technology. We pride ourselves in completing the feasibility study in a quick manner with high-quality results. Our typical approach and activities related to feasibility are mentioned below.

1. Perform Pre-Formulation Activities

Prior to manufacturing the feasibility batches, Oakwood will perform several pre-formulation activities. The results of these activities will form the methodology of how we develop a strategy for batch production.

• Evaluate solubility of the API in organic solvents and the interaction between the API and polymer
• Select initial polymer candidates based on our expertise and internal database
• Develop preliminary analytical methods to support testing of product

2. Manufacture and Characterize Feasibility Formulations

Oakwood manufactures and characterizes feasibility batches at a small scale, typically between 5-10 grams, in an iterative process of manufacturing and testing. Using the data obtained from the first batches, variation of polymer molecular weight, drug load, particle size, flow rates, and other factors that impact the release profile are tried in an iterative process.

• Manufacture microsphere formulation pilot batches
• Characterize microsphere formulation pilot batches
• Vary formulation parameters for further batches as needed

Analysis	Method
Drug Load (% drug encapsulated)	HPLC Assay
Particle Size and Volume Distribution	Laser Diffraction
Residual Solvent	Gas Chromatography
In Vitro Release	Shaker Bath or USP II/IV Apparatus, HPLC Assay

3. Finalize Feasibility Report and Select Lead Formulations for Animal Testing

Oakwood will compile all microsphere formulation data and analytical results to date in a feasibility summary report. In the report, we will recommend lead candidate formulations (usually three to five), based upon in vitro test results, for testing in animal models. Animal testing is typically conducted in dogs or rats and is outsourced. Note that in vitro release results are indicative, but are not necessarily predictive, of in vivo performance.

• Finalize feasibility summary report including all results to date
• Recommend lead formulations for animal study
• Supply material for initiating animal study

---

Next Steps for Microsphere Formulation Development

After completion of the feasibility study and animal testing, we can determine the predictive capability of the in vitro release test, and use the in vitro testing for further modification of the release profile if necessary. Additional animal testing may or may not be conducted. The microsphere formulation is then ready for initial scale-up.

If you have any additional questions about our microsphere formulation development process, or any of our other services, don’t hesitate to contact us below.