Optimum topical delivery of adrenergic agonists to oral mucosa vasculature.

PURPOSE: Identify an orotopical vehicle to deliver an α-adrenergic vasoconstrictor to submucosal vasculature that is readily palatable to cancer/bone marrow transplant patients that suppresses chemo-radiotherapy-associated oral mucositis. METHODS: A [(3)H] norepinephrine ligand binding assay was developed to quantify receptor binding in hamster oral mucosa. Vehicle components (alcohols, polyols, cellulose, PVP) were tested versus [(3)H] norepinephrine binding. Vehicle refinement was also done to mask phenylephrine bitter taste and achieve human subject acceptance. The optimized vehicle was tested with α-adrenergic active agents to suppress radiation-induced oral mucositis in mice. RESULTS: The ligand binding assay quantified dose- and time-dependent, saturable binding of [(3)H] norepinephrine. An ethanol:glycerol:propylene glycol:water (6:6:8:80) vehicle provided the best delivery and binding. Further vehicle modification (flavoring and sucralose) yielded a vehicle with excellent taste scores in humans. Addition of phenylephrine, norepinephrine or epinephrine to the optimized vehicle and painting into mouse mouths 20 min before 19 Gy irradiation conferred significant suppression of the weight loss (P < 0.001) observed in mice who received oral vehicle. CONCLUSION: We identified a highly efficient vehicle for the topical delivery of phenylephrine to the oral mucosa of both hamster and human subjects. This will enable its testing to suppress oral mucositis in an upcoming human clinical trial.

A new strategy to prevent chemotherapy and radiotherapy-induced alopecia using topically applied vasoconstrictor.

In a new strategy, we sought to determine whether topically applied vasoconstrictor, with its accompanying transient skin hypoxia and exclusion of systemic drug, would prevent or suppress radiotherapy or chemotherapy-induced alopecia. Topical vasoconstrictor was applied to 1-cm(2) skin patches on the backs of 10-day-old rats and minutes later they received either 7.1 gray (Gy) whole-body radiation or systemic N-nitroso-N-methylurea (MNU) or Cytoxan. The degree of alopecia was scored 10 days later by visual assessment (% coat retention) and hair follicle histologic analysis. Topical application of epinephrine or norepinephrine in an alcohol:water delivery vehicle induced clear skin blanch, and in a dose-dependent manner, topical epinephrine or norepinephrine (20-1,000 mM) applied before 7.1 Gy irradiation conferred 95% of coat retention in the treated skin patches versus 0% coat retention in vehicle controls, or in skin outside the treated patches. By histology, small numbers of dystrophic hair follicles were observed in hairless skin versus the normal density of anagen follicles in the immediately adjacent, drug-protected skin patches at day 20; protected coats were retained into adulthood. Topical epinephrine or norepinephrine before systemic MNU (30 ug/gm body weight) conferred up to 95% of coat retention in treated skin patches versus 0% coat retention elsewhere. Epinephrine-conferred % coat retention dropped to 16% in rats that received systemic Cytoxan, a drug whose plasma half-life is at least 8- to 10-fold longer than MNU. A general strategy is discussed for the use of topical epinephrine or norepinephrine in the clinic to provide an inexpensive and convenient strategy to prevent cancer therapy-induced alopecia.

A new topical vasoconstrictor-based strategy for prevention of oral mucositis.

OBJECTIVE: In a new strategy, we sought to determine whether vasoconstriction and transient hypoxia of the mucosa during irradiation would prevent or suppress radiation-induced oral mucositis. STUDY DESIGN: Topical vasoconstrictor was applied once to the oral cavity; 20 minutes later hamsters or mice received 19 to 30 Gy to the mucosa. Oral mucositis was scored using functional assay, gross morphology, and histology of mucosal tissue over the next 12 to 16 days. RESULTS: A single application of phenylephrine (14 mM to 136 mM) 20 minutes before irradiation conferred highly significant (P < .001), dose-dependent suppression of weight loss, oral secretion, and histopathology of mucosa seen in mice treated with 0 mM phenylephrine + 19-Gy irradiation. Epinephrine, norepinephrine, and phenylephrine showed up to 100% radioprotective efficacy at concentrations that reflected their rank-ordered affinities for the α1-adrenergic receptor. CONCLUSIONS: Phenylephrine swish-and-spit application before radiotherapy, or multiple applications during chemotherapy, may provide a simple, cost-effective strategy for suppression of oral mucositis in patients undergoing radiotherapy, chemotherapy, or bone marrow transplant.

Radioprotective efficacy and toxicity of a new family of aminothiol analogs.

PURPOSE: A family of 17 new nucleophilic-polyamine and aminothiol structures was designed and synthesized to identify new topical or systemic radioprotectors with acceptable mammalian toxicity profiles. design elements included: (i) Length and charge of the DNA-interacting, alkylamine backbone, (ii) nucleophilicity of the reactive oxygen species (ROS)-scavenging group, and (iii) non-toxic drug concentration achievable in animal tissues. MATERIALS AND METHODS: Mouse maximum tolerated doses (MTD) were determined by increasing intraperitoneal (IP) doses. To assess radioprotective efficacy, mice received IP 0.5 MTD doses prior to an LD95 radiation dose (8.63 Gy), and survival was monitored. Topically applied aminothiol was also scored for prevention of radiation-induced dermatitis (17.3 Gy to skin). RESULTS: The most radioprotective aminothiols had 4-6 carbons and 1-2 amines, and unlike amifostine and its analogs, displayed a terminal thiol from an alkyl side chain that projected the thiol away from the DNA major groove into the environment surrounding the DNA. The five carbon, single thiol, alkylamine, PrC-210, conferred 100% survival to an otherwise 100% lethal dose of whole-body radiation and achieved 100% prevention of Grade 2-3 radiation dermatitis. By mass spectrometry analysis, the one aminothiol that was tested formed mixed disulfides with cysteine and glutathione. CONCLUSIONS: Multiple, highly radioprotective, aminothiol structures, with acceptable systemic toxicities, were identified.

ROS-scavenger and radioprotective efficacy of the new PrC-210 aminothiol.

To identify new aminothiol radioprotectors that are active when applied topically and have fewer side effects when administered systemically, a new family of aminothiol radioprotectors was designed and synthesized. Three key elements in the aminothiol design were, (1) small size for efficient transmembrane diffusion, (2) positive charged amines in alkyl backbone for strong ionic interaction with DNA backbone, and (3) a perpendicular, alkyl side-chain with a terminal thiol that is projected away from the DNA backbone to enable reactive oxygen species scavenging around DNA. Several in vitro assays were used to characterize the prototype aminothiol, PrC-210, for efficacy: protection against reactive oxygen species-induced plasmid DNA nicking, mass spectrometry to detect aminothiol-reactive oxygen species by-products, S. typhimurium mutagenesis, human cell growth inhibition, Western blot for p21 expression, and FACS analysis. Additionally, two in vivo assays were used to assess radioprotective efficacy; a Sprague-Dawley rat dorsal skin radiodermatitis assay was developed to screen for aminothiol efficacy when topically applied, and ICR mouse survival was scored after systemic PrC-210 administration and whole-body radiation. PrC-210 efficiently scavenged reactive oxygen species and completely protected supercoiled plasmid DNA against reactive oxygen species-induced damage. Neither PrC-210 nor its analog PrC-211 were bacterial mutagens. In cell culture, PrC-210 application to diploid human fibroblasts showed: (1) inhibition of cell growth with an IC(70) of 4.1 mM, (2) induced levels of p21 expression, and (3) a G(1)/S-cell cycle block that was reversed after washout of PrC-210-containing medium. In rodents, PrC-210 was an effective radioprotector showing: (1) complete prevention of Grade 2-3 radiodermatitis when applied topically (370 mM in ethanol:propylene glycol:water solution) prior to skin irradiation, (2) complete prevention of Grade 2-3 radiodermatitis when administered by i.p. injection (200 µg/g of body weight) before skin irradiation, (3) 100% survival of mice from an otherwise 100% lethal dose of whole-body radiation (8.75 Gy) when administered by i.p. injection (252 µg/g of body weight = 0.5 × maximum tolerated dose) before irradiation, and (4) a dose reduction factor of 1.6, the same as amifostine. These data suggest that the PrC-210 aminothiol is a plausible candidate for drug development as a human pre-exposure radioprotector.

A new orally active, aminothiol radioprotector-free of nausea and hypotension side effects at its highest radioprotective doses.

PURPOSE: A new aminothiol, PrC-210, was tested for orally conferred radioprotection (rats, mice; 9.0 Gy whole-body, which was otherwise lethal to 100% of the animals) and presence of the debilitating side effects (nausea/vomiting, hypotension/fainting) that restrict use of the current aminothiol, amifostine (Ethyol, WR-2721). METHODS AND MATERIALS: PrC-210 in water was administered to rats and mice at times before irradiation, and percent-survival was recorded for 60 days. Subcutaneous (SC) amifostine (positive control) or SC PrC-210 was administered to ferrets (Mustela putorius furo) and retching/emesis responses were recorded. Intraperitoneal amifostine (positive control) or PrC-210 was administered to arterial cannulated rats to score drug-induced hypotension. RESULTS: Oral PrC-210 conferred 100% survival in rat and mouse models against an otherwise 100% lethal whole-body radiation dose (9.0 Gy). Oral PrC-210, administered by gavage 30-90 min before irradiation, conferred a broad window of radioprotection. The comparison of PrC-210 and amifostine side effects was striking because there was no retching or emesis in 10 ferrets treated with PrC-210 and no induced hypotension in arterial cannulated rats treated with PrC-210. The tested PrC-210 doses were the ferret and rat equivalent doses of the 0.5 maximum tolerated dose (MTD) PrC-210 dose in mice. The human equivalent of this mouse 0.5 MTD PrC-210 dose would likely be the highest PrC-210 dose used in humans. By comparison, the mouse 0.5 MTD amifostine dose, 400 µg/g body weight (equivalent to the human amifostine dose of 910 mg/m(2)), when tested at equivalent ferret and rat doses in the above models produced 100% retching/vomiting in ferrets and 100% incidence of significant, progressive hypotension in rats. CONCLUSIONS: The PrC-210 aminothiol, with no detectable nausea/vomiting or hypotension side effects in these preclinical models, is a logical candidate for human drug development to use in healthy humans in a wide variety of radioprotection settings, including medical radiation, space travel, and nuclear accidents.