Ahmad P. Samiee

Transdermal Delivery of Antisense Oligonucleotides with Microprojection Patch (macroflux®) Technology

In recent years, antisense oligodeoxynucleotide (ODN) technology has emerged as one of the most promising functional genomic therapies. Several clinical trials have demonstrated its therapeutic value and low toxicity (1). To date, parenteral infusion has been the primary mode of ODN delivery. However, efforts to develop more convenient routes of administration are being explored. Transdermal iontophoresis increased ODNs across the skin; however, delivery of a therapeutically relevant dose was not achieved (2–5). The major barrier for transdermal delivery is the stratum corneum, the outermost “dead” layer of the skin. In human skin, the stratum corneum is 10–20 m thick, whereas in mice and rats it is significantly thinner. Removal of the stratum corneum by mechanical abrasion, tape stripping, or chemical treatment has been shown to significantly enhance permeation through the skin for a wide range of pharmaceuticals, including phosphorothioated (PS) ODNs (5–8). However, these approaches may be limited due to the lack of control and reproducibility, as well as the irritancy potential (9). Microprojection patch is a novel microfabrication technology for controlled transdermal drug delivery. The patch system incorporates a stainless steel or titanium microprojection array. When applied onto the skin manually or by an applicator, microprojections penetrate and create superficial pathways through the skin barrier layer to allow drug delivery. The array can be combined either with passive or iontophoretic delivery systems. In this study, we demonstrate that microprojection patch technology can facilitate the controlled transdermal ODN delivery. MATERIALS AND METHODS

Human Growth Hormone Delivery with a Microneedle Transdermal System: Preclinical Formulation, Stability, Delivery and PK of Therapeutically Relevant Doses

This study evaluated the feasibility of coating formulated recombinant human growth hormone (rhGH) on a titanium microneedle transdermal delivery system, Zosano Pharma (ZP)-hGH, and assessed preclinical patch delivery performance. Formulation rheology and surface activity were assessed by viscometry and contact angle measurement. rhGH liquid formulation was coated onto titanium microneedles by dip-coating and drying. The stability of coated rhGH was determined by size exclusion chromatography-high performance liquid chromatography (SEC-HPLC). Preclinical delivery and pharmacokinetic studies were conducted in female hairless guinea pigs (HGP) using rhGH coated microneedle patches at 0.5 and 1 mg doses and compared to Norditropin® a commercially approved rhGH subcutaneous injection. Studies demonstrated successful rhGH formulation development and coating on microneedle arrays. The ZP-hGH patches remained stable at 40 °C for six months with no significant change in % aggregates. Pharmacokinetic studies showed that the rhGH-coated microneedle patches, delivered with high efficiency and the doses delivered indicated linearity with average Tmax of 30 min. The absolute bioavailability of the microneedle rhGH patches was similar to subcutaneous Norditropin® injections. These results suggest that ZP-transdermal microneedle patch delivery of rhGH is feasible and may offer an effective and patient-friendly alternative to currently marketed rhGH injectables.