Table 2. Thermoresponsive biodegradable injectable drug delivery systems.

	AtriGel®	ReGel™	LiquoGel™
Description	Polymer (1 unit) for physically delivering entrapped pharmaceuticals	Copolymer (3 units) for physically delivering entrapped pharmaceuticals	Copolymer (4 units) for physically delivering entrapped and/or covalently linked pharmaceuticals
Properties	Water-insoluble Biodegradable Liquid: < 0°C – 30°C Gel: 37°C	Water soluble Biodegradable Liquid: < 0°C – 30°C Gel: 37°C	Water soluble Biodegradable Liquid: <4°C – 30°C Gel: 37°C
Mechanism of Drug Release	Diffusion and polymer erosion	Diffusion and polymer erosion	Diffusion and polymer erosion
Drug Release Delay	4–6 weeks	6–8 weeks	12–15 hours
Composition	Polymer platform consisting of one of the following: PLA 1, PLG 2, PLC 3, PAH 4	Triblock copolymer of: PLGA-PEG-PLGA	4 Components: Acrylic Acid Polyglycerol N-Isopropylaniline HEMA-Lac 5 HPG-MA 6
Recent applications	Testosterone reduced: Clinical studies using a depot containing 22.5 mg leuprolide maintained an effective suppression of serum testosterone (50 ng/dL) for more than 3 months.	Cancer: Single drugs were incorporated including paclitaxel, porcine growth hormone, glucagon-like peptide-1 (GLP-1), interleukin 2 (IL-2) and G-CSF	Uterine Fibroids: In Development

Notes: ¹poly(DL-lactide); ²poly(DL-lactide-do-glycolide); ³poly(DL-lactide-co-caprolactone); ⁴polyanydrides; ⁵hydroxyethyl methacrylate-polylactide; ⁶Hyperbranched polyglycerol. Modified from reference 23