Pharmacokinetics and toxicity of subcutaneous administration of carboplatin in poloxamer 407 in a rodent model pilot study

<div><p>The objectives of this study were to assess the pharmacokinetics and safety of subcutaneously delivered carboplatin in poloxamer 407 in rats. Carboplatin (5mg/rat) in 0.5ml poloxamer 407 (1.0 ml total volume) was administered subcutaneously in a right subcutaneous perineal incision in all 12 treatment rats. Three control rats received 1.0 ml of poloxamer 407. Total platinum was measured in plasma q24hrs from 0 to 168hrs. Protein-unbound platinum was measured in plasma at 168hrs. After sacrifice on day 7, total platinum was determined in wound bed muscle. Platinum concentrations in all samples were measured by ICP-MS. Wounds were visually assessed daily for 7 days. Perineal tissues (full wound bed including muscle, subcutis, skin) were assessed histologically and scored. Total platinum was detectable in plasma from 24 to 168 hrs. Total plasma platinum AUC and C_max were 9,165.3 ng/mL•h and 129.4 ng/mL. Day 7 total platinum concentration in muscle was approximately 10-fold higher than total plasma platinum concentration. No unbound platinum was detected in plasma samples at 168 hours. No wound healing complications were detected at any time point, nor was tissue necrosis observed histologically. The results of this study suggest that subcutaneous carboplatin in poloxamer 407 can be used in vivo providing direct tissue exposure to carboplatin without significant local effects or systemic absorption and without wound healing complications.</p></div

Non-compartmental pharmacokinetic parameter of Pt.

<p>Non-compartmental pharmacokinetic parameter of Pt.</p

Concentration of total Pt in plasma and total Pt in muscle at 168 hrs.

<p>The carboplatin concentration (ng/mL) is plotted on the Y-axis in a logarithmic scale. ‘●’ and ‘▼’ represent the Ptplasma (n = 11)and Ptmuscle (n = 6) of every individual rat, respectively.</p

Histological scores.

<p>Histological scores.</p

Histology of the subcutaneous perineal implantation site.

<p>A Shows a photomicrograph of the subcutaneous perineal surgical implantation site of rat from the CP cohort. Minimal necrosis of adipose (score = 1) (arrow) is present adjacent to the implantation site (asterisk). B Shows a photomicrograph of the subcutaneous perineal surgical implantation site of a rat from the CP-μD cohort. Minimal fibrosis (score = 1) (arrows) is present adjacent to the implantation site (asterisk) after receiving carboplatin and poloxamer 407 gel and a μD catheter (C) at the site.</p

Ultrastructural findings for 3-month-old puppies with ectodermal dysplasia-skin fragility syndrome and PKP1 deficiency.

<p>Panel A: Transmission electron microscopy of carpal pad epidermis reveals widening of intercellular spaces between keratinocytes and retraction of keratin filaments from the cell membrane. Panel B: Higher magnification photomicrograph (Box insert from Panel A) demonstrates reduced numbers of desmosomes attaching keratinocytes as well as the presence of small, partially formed desmosomes (arrows). Panels C and D: A higher magnification confirms that desmosomes appear small and rudimentary in an affected dog (C) compared to those of a normal dog (D). Bar = 1 µm.</p

Histopathology findings for 3-month-old puppies with ectodermal dysplasia-skin fragility syndrome and PKP1 deficiency.

<p>Panel A: Trunk skin exhibits diffuse epidermal hyperplasia topped by prominent, laminated to compact, orthokeratotic hyperkeratosis. Panel B: Higher magnification photomicrograph (Box insert from Panel A) illustrates mild keratinocyte acantholysis (arrows) in the stratum granulosum as well as condensation and aggregation of eosinophilic tonofilaments in the cytoplasm (arrow head). Panel C: Similar changes of keratinocyte acantholysis (arrows) and condensation of tonofilaments (arrowheads) are observed in the carpal pad epidermis. Hematoxylin and eosin. Bar = 100 µm.</p

Expression of selected keratin and desmosomes proteins in normal and affected Chesapeake Bay retriever dogs.

<p>Panels A–D: normal age- and breed-matched control dog footpad E–H: affected dog footpad. Panels A, E: keratin K14 was expressed in the cytoplasm of basal keratinocytes of both affected and normal dogs, but the staining pattern was more heterogeneous in affected dogs; some mid-epidermal keratinocytes expressed K14 in affected but not normal dogs. Panels B, F: in normal dogs, keratin K10 was seen with an homogeneous staining in suprabasal keratinocytes (B); in affected dogs, the staining intensity was heterogeneous within and between keratinocytes. Panels C, G: desmoplakin (DSP) staining revealed a typical fishnet intercellular pattern in normal dog skin (C), while it was cytoplasmic and heterogeneous in affected dogs (G). Panels D, H: Using the monoclonal antibody specific for armadillo-repeats of plakophilin-1 (PKP1), this molecule was detected intercellularly, with a dotted pattern, in the superficial epidermis of the normal control CBR (D); this pattern was not seen in samples from affected dogs (H). All panels were shot at ×20 magnification.</p

Mutation in <i>PKP1</i> causing ED-SFS in Chesapeake Bay retrievers.

<p>Panel A: Transition from G-to-C at intronic splice donor site at the beginning of the first intron ([G/C]). Panel B. Consequence of the mutation described in panel A. The intronic splice donor site is destroyed by the transition from a G to a C resulting in a continual read through to a premature stop codon. Nucleotides in capitals are from exon 1 and those in small letters from intron 1.</p

Histopathology findings for neonatal puppies with ectodermal dysplasia-skin fragility syndrome and PKP1 deficiency.

<p>Panel A: coalescing keratinocyte acantholysis disrupts epidermal architecture in a biopsy from the distal limb with prominent involvement of the stratum spinosum. At higher magnification (insert), individual acantholytic keratinocytes (arrows) are rounded and have retraction and condensation of eosinophilic tonofilaments within the cytoplasm. Hematoxylin and eosin. Panel B: in normal canine skin, the epidermis consists of keratinocytes abutting each other at all layers. Bar = 100 µm.</p