Innovative HPMC/PVP K90 Dissolving Microneedles Incorporating Tacrolimus-Loaded Cubosomes: A Novel Strategy for Managing Allergic Conjunctivitis

Background/Objectives: Allergic conjunctivitis (AC) is the most common inflammatory disease affecting the ocular conjunctiva. Tacrolimus (TCR), a potent calcineurin inhibitor, is limited by poor aqueous solubility and low ocular bioavailability. This study aimed to develop TCR-loaded cubosomes (TCR-Cubs) incorporated into HPMC/PVP K90 dissolving microneedles (MNs) to enhance their therapeutic efficacy. Methods: TCR-Cubs were prepared using a modified top-down fragmentation method with glyceryl monooleate and poloxamer 407, optimized via Box–Behnken design, and incorporated into dissolving MNs. The system was evaluated in vitro, ex vivo, and in vivo using a rabbit model of allergic conjunctivitis. Results: The optimized formulation exhibited the smallest particle size (210 ± 0.91 nm), polydispersity index (0.29 ± 0.03), zeta potential (−21 ± 0.87 mV), and the highest entrapment efficiency (% 93.3 ± 0.45). The optimized formulation was incorporated into MNs via micro molding. Scanning electron microscopy (SEM) confirmed well-defined, sharp microneedles, with low height reduction (85–90%). In vitro release studies revealed sustained drug release of (~75–80%) over 24 h, compared to (~40%) from the TCR suspension, following diffusion-controlled kinetics. Ex vivo permeation studies showed a (~2–3-fold) enhancement in corneal drug flux. In vivo pharmacodynamic evaluation using an ovalbumin-induced allergic conjunctivitis model demonstrated significant reductions in inflammatory mediators, including inflammatory markers (TNF-α, IL-1β, IL-6, NLRP3), which were reduced by (~50–75%), with modulation of CPA3, BCL2, and TGF-β1 by qRT-PCR. Histopathology and TLR4 analysis confirmed reduced inflammation without irritation. Conclusions: This dual-delivery system offers a promising, non-invasive platform for enhanced ocular delivery of tacrolimus with superior anti-inflammatory efficacy in allergic conjunctivitis.