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Local Effects Following Single and Repeat Intra-Articular Injections of Triamcinolone Acetonide Extended-Release: Results from Three Nonclinical Toxicity Studies in Dogs.

ABSTRACT:

Introduction

Single intra-articular (IA) injections of poly(lactic-co-glycolic acid) (PLGA) microsphere-based triamcinolone acetonide extended-release (TA-ER; formerly FX006) demonstrated sustained, clinically relevant benefits in patients with knee osteoarthritis. The local effects of TA-ER were assessed in normal canine knees in three nonclinical studies.

Methods

Knees were evaluated for up to 6 weeks or 9 months after a single injection of TA-ER (2.1/6.25/18.75 mg TA), or TA crystalline suspension (TAcs, 18.75 mg TA), and for up to 6 months after three injections (every 1 or 3 months) of TA-ER (6.25/18.75 mg TA) or TAcs (18.75 mg). Vehicle-diluent, blank microspheres, and untreated knees were used as controls. Plasma and synovial fluid (SF) TA concentrations and standard histopathological assessment of the synovium were conducted. Articular cartilage morphology was assessed via modified Mankin scoring.

Results

Plasma and SF concentrations indicated prolonged dose-dependent TA joint residency with TA-ER compared with TAcs. Effects in articular cartilage were dose- and time-dependent and consistent with known effects of corticosteroids in the normal knee. Loss of Safranin O staining occurred, indicative of a reduction in cartilage matrix proteoglycan, and recovered in a similar manner for TA-ER and TAcs across all studies. Structural lesions were infrequent and generally comparable in severity between TA-ER and TAcs but slightly higher in incidence for TA-ER. Focal/multifocal foreign-body responses (FBR) to PLGA were observed in the superficial layer of the synovium, peaking after 4-6 weeks, with significant recovery or complete resolution by month 6.

Conclusions

These findings suggest that the effects of IA injections of TA-ER on cartilage are predominantly transient, and comparable to those observed with TAcs in the normal canine knee joint. These mild effects in the normal joint differ from the beneficial effects observed with TA-ER and other corticosteroids in disease models. The synovial FBR to PLGA microspheres was focal and transient.

Funding

Flexion Therapeutics, Inc. Plain language summary available for this article.

SUBMITTER: Bodick N

PROVIDER: S-EPMC6251841 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundIntra-articular corticosteroids are commonly used for pain relief in patients with knee osteoarthritis. Simultaneous intra-articular corticosteroid (CS) knee injections may be beneficial for the ~80-90% of patients who present with, or develop, bilateral knee osteoarthritis, but concurrent injections may increase systemic CS exposure and data on safety/tolerability are lacking. Triamcinolone acetonide extended release (TA-ER) has shown decreased systemic triamcinolone acetonide exposure compared with traditional triamcinolone acetonide crystalline suspension (TAcs) after a single knee injection in patients with knee osteoarthritis. This phase IIa study was designed to assess the safety and systemic triamcinolone acetonide exposure following injections of TA-ER or TAcs into each knee of patients with bilateral knee osteoarthritis.MethodsPatients (⩾40 years) meeting American College of Rheumatology criteria for knee osteoarthritis in both knees received concurrent single intra-articular injections of TA-ER 32 mg or TAcs 40 mg into each knee (total: 64 mg and 80 mg, respectively) and were followed for 6 weeks. Safety was evaluated based on treatment-emergent adverse events (TEAEs). Blood samples for pharmacokinetic analysis were collected pre-injection, and at the following postinjection time points: 1, 2, 3, 4, 5, 6, 8, 10, 12, and 24 h, and days 8, 15, 29, and 43.ResultsBaseline characteristics were balanced between patients randomly assigned to TA-ER (n = 12) or TAcs (n = 12). Both treatments were well tolerated with comparable TEAE profiles. Peak plasma triamcinolone acetonide concentrations (Cmax) were lower following bilateral TA-ER injections [geometric mean, 2277.7 pg/ml (95% CI, 1602.13-3238.04)] compared with bilateral TAcs injections [7394.7 pg/ml (2201.06-24,843.43)], with median times to Cmax (Tmax) of 4.5 and 6.5 h, respectively.ConclusionsIn patients with bilateral knee osteoarthritis, intra-articular injection of TA-ER into both knees was well tolerated. Consistent with pharmacokinetic profiles observed after a single knee injection, plasma triamcinolone acetonide concentrations were lower after bilateral TA-ER injections compared with the higher and more variable concentrations observed after bilateral TAcs injections.Clinicaltrialsgov identifierNCT03378076.

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