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Excessive adipose tissue macrophage accumulation in obesity has been implicated in mediating inflammatory responses that impair glucose homeostasis and promote insulin resistance. Colony-stimulating factor 1 (CSF1) controls macrophage differentiation, and here we sought to determine the effect of a CSF1 receptor inhibitor, PLX3397, on adipose tissue macrophage levels and understand the impact on glucose homeostasis in mice. A Ten-week-old mice were fed a chow or high-fat diet for 10 weeks and then treated with PLX3397 via oral gavage (50 mg/kg) every second day for 3 weeks, with subsequent monitoring of glucose tolerance, insulin sensitivity and assessment of adipose tissue immune cells. PLX3397 treatment substantially reduced macrophage numbers in adipose tissue of both chow and high-fat diet fed mice without affecting total myeloid cell levels. Despite this, PLX3397 did not greatly alter glucose homeostasis, did not affect high-fat diet-induced increases in visceral fat cytokine expression (Il-6 and Tnfa) and had limited effect on the phosphorylation of the stress kinases JNK and ERK and macrophage polarization. Our results indicate that macrophage infiltration of adipose tissue induced by a high-fat diet may not be the trigger for impairments in whole body glucose homeostasis, and that anti-CSF1 therapies are not likely to be useful as treatments for insulin resistance.

The structure-activity relationships for a series of arylsulphonamide-based inhibitors of the pore-forming protein perforin have been explored. Perforin is a key component of the human immune response, however inappropriate activity has also been implicated in certain auto-immune and therapy-induced conditions such as allograft rejection and graft versus host disease. Since perforin is expressed exclusively by cells of the immune system, inhibition of this protein would be a highly selective strategy for the immunosuppressive treatment of these disorders. Compounds from this series were demonstrated to be potent inhibitors of the lytic action of both isolated recombinant perforin and perforin secreted by natural killer cells in vitro. Several potent and soluble examples were assessed for in vivo pharmacokinetic properties and found to be suitable for progression to an in vivo model of transplant rejection., final draft, peerReviewed

The present study reports on the development of a hybrid system by integrating poly(lactic- co -glycolic)acid nanoparticles (PLGA NPs) into light-responsive in-situ forming injectable implants (ISFIs) for minimally invasive and safe intravitreal peptide delivery. In the first part of the study, peptide-loaded PLGA based nanoparticles (NPs) were developed using the two-step nanoprecipitation technique. Peptide compatibility with PLGA and polyvinyl alcohol was confirmed via IR spectroscopy. Developed NPs had a size of 149.3–235.4 nm, a polydispersity index between 0.24 and 0.46, a zeta potential of −32.4 to −27.0 mV and an entrapment efficiency of 34.3–55.3%. In the second part of the study, successful synthesis of methacrylated alginate (MA) and its subsequent photocrosslinking upon photoirridiation was confirmed by 1 H NMR. Photocrosslinked MA exhibited the required clarity and its gelling time, morphology, syringeability, hardness, rate of swelling and degradation were found suitable for prolonging its residence in the posterior segment. The sulforhodamine B assay on human retinal pigment epithelium cells and the zebrafish embryo toxicity test confirmed the biocompatibility of NPs and ISFIs. Finally, NPs were incorporated into the ISFIs for improved particle retention and to further sustain drug release, suggesting the proposed hybrid system as an innovative and efficient ocular drug delivery platform.

Diseases affecting the posterior segment the eye, such as age-related macular degeneration (AMD), are the leading cause of blindness worldwide. Conventional dosage forms, such as eye drops, have to surmount several elimination mechanisms and complex barriers to achieve therapeutic concentrations at the target site often resulting in low anterior segment bioavailability (ca. 2-5%) with generally none of the drug reaching posterior segment tissues. Thus, frequent intravitreal injections are currently required to treat retinal conditions which have been associated with poor patient compliance due to pain, risk of infection, hemorrhages, retinal detachment and high treatment related costs. To partially overcome these issues, ocular implants have been developed for some posterior segment indications; however, the majority require surgical implantation and removal at the end of the intended treatment period. The transparent nature of the cornea and lens render light-responsive systems an attractive strategy for the management of diseases affecting the back of the eye. Light-responsive in situ forming injectable implants (ISFIs) offer various benefits such as ease of application in a minimally invasive manner and more site specific control over drug release. Moreover, the biodegradable nature of such implants avoids the need for surgical removal after release of the payload. Incorporating drug-loaded polymeric nanoparticles (NPs) into these implants may reduce the high initial burst release from the polymeric matrix and further sustain drug release thus avoiding the need for frequent injections as well as minimizing associated side effects. However, light-responsive systems for ophthalmic application are still in their early stages of development with limited reports on their safety and effectiveness. We hypothesize that the innovative design and properties of NP-containing light-responsive ISFIs can serve as a platform for effective management of ocular diseases requiring long term treatment.

The pore-forming protein perforin is a key component of mammalian cell-mediated immunity and essential to the pathway that allows elimination of virus-infected and transformed cells. Perforin activity has also been implicated in certain auto-immune conditions and therapy-induced conditions such as allograft rejection and graft versus host disease. An inhibitor of perforin activity could be used as a highly specific immunosuppressive treatment for these conditions, with reduced side-effects compared to currently accepted therapies. Previously identified first-in-class inhibitors based on a 2-thioxoimidazolidin-4-one core show suboptimal physicochemical properties and toxicity toward the natural killer (NK) cells that secrete perforin in vivo. The current benzenesulphonamide-based series delivers a non-toxic bioisosteric replacement possessing improved solubility., published version, peerReviewed

Hypoxia-activated prodrugs (HAPs) are hypothesized to improve the therapeutic index of chemotherapy drugs that are ineffective against tumor cells in hypoxic microenvironments. SN30000 (CEN-209) is a benzotriazine di-N-oxide HAP that potentiates radiotherapy in preclinical models, but its combination with chemotherapy has not been explored. Here we apply multiple models (monolayers, multicellular spheroids and tumor xenografts) to identify promising SN30000/chemotherapy combinations (with chemotherapy drugs before, during or after SN30000 exposure). SN30000, unlike doxorubicin, cisplatin, gemcitabine or paclitaxel, was more active against cells in spheroids than monolayers by clonogenic assay. Combinations of SN30000 and chemotherapy drugs in HCT116/GFP and SiHa spheroids demonstrated hypoxia-and schedule-dependent potentiation of gemcitabine or doxorubicin in growth inhibition and clonogenic assays. Co-administration with SN30000 suppressed clearance of gemcitabine in NIH-III mice, likely due to SN30000-induced hypothermia which also modulated extravascular transport of gemcitabine in tumor tissue as assessed from its diffusion through HCT116 multicellular layer cultures. Despite these systemic effects, the same schedules that gave therapeutic synergy in spheroids (SN30000 3 h before or during gemcitabine, but not gemcitabine 3 h before SN30000) enhanced growth delay of HCT116 xenografts without increasing host toxicity. Identification of hypoxic and S-phase cells by immunohistochemistry and flow cytometry established that hypoxic cells initially spared by gemcitabine subsequently reoxygenate and re-enter the cell cycle, and that this repopulation is prevented by SN30000 only when administered with or before gemcitabine. This illustrates the value of spheroids in modeling tumor microenvironment-dependent drug interactions, and the potential of HAPs for overcoming hypoxia-mediated drug resistance.

BYL719 (alpelisib) is a small molecule inhibitor of PI3K p110&alpha, developed for cancer therapy. Targeted suppression of PI3K has led to lifespan extension in rodents and model organisms. If PI3K inhibitors are to be considered as an aging therapeutic, it is important to understand the potential consequences of long-term exposure, and the most practical way to achieve this is through diet administration. Here, we investigated the pharmacokinetics of BYL719 delivered in diet and the efficacy of BYL719 to suppress insulin signaling when administered in the diet of 8-month-old male and female mice. Compared to oral gavage, diet incorporation resulted in a lower peak plasma BYL719 (3.6 vs. 9.2 &mu, M) concentration but similar half-life (~1.5 h). Consuming BYL719 resulted in decreased insulin signaling in liver and muscle within 72 h, and mice still showed impaired glucose tolerance and insulin sensitivity following 6 weeks of access to a diet containing 0.3 g/kg BYL719. However, consuming BYL719 did not affect food intake, body mass, muscle function (rotarod and hang time performance) or cognitive behaviors. This provides evidence that BYL719 has long-term efficacy without major toxicity or side effects, and suggests that administering BYL719 in diet is suitable for studying the effect of pharmacological suppression of PI3K p110&alpha, on aging and metabolic function.

Frequent intravitreal injections are currently the preferred treatment method for diseases affecting the posterior segment of the eye. However, these repeated injections have been associated with pain, risk of infection, hemorrhages, retinal detachment and high treatment costs. To overcome these limitations, light-responsive in situ forming injectable implants (ISFIs) may emerge as novel systems providing site-specific controlled drug delivery to the retinal tissues with great accuracy, safety, minimal invasiveness and high cost efficiency.Complex ocular barriers, routes for drug delivery, types of injectable implants, ocular application of light and benefits of light-responsive systems are discussed with regards to challenges and strategies employed for effective drug delivery to the posterior segment of the eye. In particular, we have highlighted photoresponsive moieties, photopolymerization mechanisms and different development strategies with their limitations as well as recent advancements in the field.Biodegradable light-responsive ISFIs are promising drug delivery systems that have shown a high degree of biocompatibility with sustained drug release in a number of applications. However, their use in intravitreal drug delivery is still in the very early stages. Issues related to the biocompatibility of the photoinitiator and the elimination of photo-degraded by-products from the ocular tissues need careful consideration, not only from a chemistry standpoint, but also from a biological perspective to improve the suitability of these systems for clinical applications.

Graphical abstract, Evolution from a furan-containing high-throughput screen (HTS) hit (1) resulted in isobenzofuran-1(3H)-one (2) as a potent inhibitor of the function of both isolated perforin protein and perforin delivered in situ by intact KHYG-1 NK cells. In the current study, structure–activity relationship (SAR) development towards a novel series of diarylthiophene analogues has continued through the use of substituted-benzene and -pyridyl moieties as bioisosteres for 2-thioxoimidazolidin-4-one (A) on a thiophene (B) -isobenzofuranone (C) scaffold. The resulting compounds were tested for their ability to inhibit perforin lytic activity in vitro. Carboxamide (23) shows a 4-fold increase over (2) in lytic activity against isolated perforin and provides good rationale for continued development within this class.

Effective drug delivery to the retina still remains a challenge due to ocular elimination mechanisms and complex barriers that selectively limit the entry of drugs into the eye. To overcome these barriers, frequent intravitreal injections are currently used to achieve high drug concentrations in vitreous and retina. However, these repetitive injections may result in several side effects. Recent advancements in the field of nanoparticle-based drug delivery could overcome some of these unmet needs and various preclinical studies conducted to date have demonstrated promising results of nanotherapies in the treatment of retinal diseases. Compared to the majority of commercially available ocular implants, the biodegradable nature of most nanoparticles (NPs) avoids the need for surgical implantation and removal after the release of the payload. In addition, the sustained drug release from NPs over an extended period of time reduces the need for frequent intravitreal injections and the risk of associated side effects. The nanometer size and highly modifiable surface properties make NPs excellent candidates for targeted ocular drug delivery. Studies have shown that nanocarriers enhance the intravitreal half-life and thus bioavailability of a number of drugs including proteins and peptides. In addition, they have shown promising results in delivering genetic material to the retinal tissues by protecting it from possible intravitreal degradation. This review covers the various challenges associated with drug delivery to the posterior segment of the eye, particularly the retina, and highlights the application of nanocarriers to overcome these challenges in context with recent advances in preclinical studies. WIREs Nanomed Nanobiotechnol 2018, 10:e1473. doi: 10.1002/wnan.1473 This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Purpose: Tirapazamine (TPZ) has attractive features for targeting hypoxic cells in tumors but has limited clinical activity, in part because of poor extravascular penetration. Here, we identify improved TPZ analogues by using a spatially resolved pharmacokinetic/pharmacodynamic (SR-PKPD) model that considers tissue penetration explicitly during lead optimization. Experimental design: The SR-PKPD model was used to guide the progression of 281 TPZ analogues through a hierarchical screen. For compounds exceeding hypoxic selectivity thresholds in single-cell cultures, SR-PKPD model parameters (kinetics of bioreductive metabolism, clonogenic cell killing potency, diffusion coefficients in multicellular layers, and plasma pharmacokinetics at well tolerated doses in mice) were measured to prioritize testing in xenograft models in combination with radiation. Results: SR-PKPD–guided lead optimization identified SN29751 and SN30000 as the most promising hypoxic cytotoxins from two different structural subseries. Both were reduced to the corresponding 1-oxide selectively under hypoxia by HT29 cells, with an oxygen dependence quantitatively similar to that of TPZ. SN30000, in particular, showed higher hypoxic potency and selectivity than TPZ in tumor cell cultures and faster diffusion through HT29 and SiHa multicellular layers. Both compounds also provided superior plasma PK in mice and rats at equivalent toxicity. In agreement with SR-PKPD predictions, both were more active than TPZ with single dose or fractionated radiation against multiple human tumor xenografts. Conclusions: SN30000 and SN29751 are improved TPZ analogues with potential for targeting tumor hypoxia in humans. Novel SR-PKPD modeling approaches can be used for lead optimization during anticancer drug development. Clin Cancer Res; 16(20); 4946–57. ©2010 AACR.

This study was carried out to explore the effect of piperine-containing food in altering the pharmacokinetics of phenytoin, an anti-epileptic drug with a narrow therapeutic index. A preliminary pharmacokinetic study was carried out in mice by administering phenytoin (10 mg) orally, with or without piperine (0.6 mg). Subsequently, oral pharmacokinetics of phenytoin was carried out in six healthy volunteers in a crossover design. Phenytoin tablet (300 mg) was given 30 minutes after ingestion of a soup (melahu rasam) with or without black pepper. A further study of intavenous pharmacokinetics of phenytoin (1 mg) in rats with or without oral pretreatment with piperine (10 mg) was also conducted. The phenytoin concentration in the serum was analyzed by HPLC. The study showed a significant increase in the kinetic estimates of Ka, AUC(0-10) and AUC(0-infinity) in the piperine-fed mice. Similarly, in human volunteers piperine increased Ka, AUC(0-48), AUC(0-infinity), and delayed elimination of phenytoin. Intravenous phenytoin in the oral piperine-treated rat group showed a significant alteration in the elimination phase indicating its metabolic blockade. The significance of this finding in epileptic patients maintained on phenytoin therapy requires further investigation. This study may also have implications in the case of other drugs having a low therapeutic index.

Meloxicam, a non-steroidal anti-inflammatory drug, is a preferential inhibitor of cyclooxygenase-2 and has demonstrated potent analgesic and anti-inflammatory activity after oral administration. The present work was carried out to elucidate the anti-inflammatory and analgesic activity of a newer topical gel formulation of meloxicam (1% w/w gel) and compare it with 0.5% w/w piroxicam and 1% w/w diclofenac gels in experimental animal models. The study was also extended to determine the pharmacokinetic profile of a newer formulation of meloxicam gel after topical application on depilated skin of rats. The anti-inflammatory activities of meloxicam, piroxicam and diclofenac gels were compared using carrageenan-induced acute paw oedema and complete Freund’s adjuvant-induced chronic paw oedema in rats. Meloxicam gel showed increased protection against inflammation as compared to piroxicam and diclofenac gels. Acetic acid-induced writhing and formalin-induced phase I and phase II pain models were used to compare their analgesic activity. Meloxicam gel showed significant protection in formalin-induced phase II pain whereas its analgesic activity was less as compared to diclofenac and piroxicam gels in writhing test and formalin-induced phase I pain. The pharmacokinetic studies showed peak plasma drug concentration (Cmax) of 48.48 ± 6.57 µg/ml at 2 h (Tmax) after topical application of 500 mg of meloxicam gel formulation. The area under the curve as calculated from 0 to 6 h was found to be 114.18 ± 4.23 and 194.13 ± 3.78 µg·h/ml for 0 to ∝. The results indicate that topical preparation of meloxicam could be an effective alternative to diclofenac and piroxicam gels in inflammatory conditions and its associated pain with the possibility of less systemic side-effects.

The objective of our experiment was to study the pharmacokinetics of plain and liposome-encapsulated fluconazole after an intravitreal injection (100 microg/0.1 ml) in rabbit eyes. Equal concentrations of plain and liposome-entrapped fluconazole were injected intravitreally into albino rabbits through the pars plana after intravenous pentobarbitone anesthesia. The rabbits were sacrificed at various time intervals, and the concentration of fluconazole in vitreous, retina-choroid, aqueous humor and cornea was estimated using High Performance Liquid Chromatography (HPLC). Plain fluconazole showed a rapid vitreal clearance and a short half-life (3.08 hr), whereas liposome-entrapped fluconazole showed a longer half-life (23.40 hr). The terminal elimination constant (Ke) of the liposome-loaded drug from the vitreous was seven times less than the plain drug. In the plain fluconazole group, at 1 hr, a high concentration of the drug was found in the retina. To conclude, the elimination of fluconazole was primarily transretinal and was very rapid. Liposome encapsulation significantly increased the half-life of fluconazole in the vitreous cavity.

Purpose: To study the efficacy of intravitreally injected plain and liposome encapsulated fluconazole in the doses of 100 and 200 Ψg in Candidal endophthalmitis in rabbit eyes. Method: Endophthalmitis was induced by injecting Candida albicans (1000 CFU/0.1 ml). Seventy two hours after inoculation, plain and liposome encapsulated fluconazole (REVs) were injected. At day 16 sterility was studied using vitreous culture. Results: In the 100 & 200 Ψg plain fluconazole group, vitreous sterility was seen in 62.5% and 75%, respectively. In the liposome entrapped fluconazole a culture sterility of 25% and 50% for 100 Ψg and 200 Ψg, respectively, was seen. Conclusion: Plain fluconazole in the dose of 100 and 200 Ψg was equally effective against Candidal endophthalmitis in rabbits, but a failure of 25–37.5% of the eyes to respond, discourages one from using fluconazole as a sole therapy. Liposome entrapped fluconazole was found to be inferior to plain fluconazole in this model.

A simple, HPLC method was developed to estimate meloxicam (COX-2 inhibitor) using piroxicam as the internal standard. The mobile phase containing methanol, acetonitrile and an aqueous solution of diammonium hydrogenorthophosphate (50 mM) in the ratio of 4:1:5 was pumped at the rate 1 ml/min. Lichrocart RP-18 (125 x 4 mm) was used as an analytical column and the analytes were detected at 364 nm using a UV detector. Acidified plasma samples were extracted with chloroform, evaporated to dryness, reconstituted in the mobile phase and then a volume of 10 microl of the prepared sample was injected in the column. The retention time of meloxicam and piroxicam was found to be 2.7 and 1.9, respectively. This method showed an accuracy of 102.3% at 0.52 microg/ml and was capable of detecting a minimum concentration of 0.029 microg/ml meloxicam from biological samples. The analytical method was successfully utilized for estimating meloxicam in biological samples.

PR610 is a hypoxia-selective irreversible Human Epidermal Growth Factor Receptor (HER) family inhibitor currently in phase I clinical trials in New Zealand and the USA (clinical trial ID NCT01631279). The prodrug PR610 releases the TKI (Tyrosine Kinase Inhibitor) PR610E, a picomolar irreversible inhibitor of EGFR (HER1), under oxygen-limiting conditions typically found in solid tumors. Human neoplastic cell lines exposed to PR610 show an anoxia-selective anti-proliferative response that is associated with G1 arrest and induction of apoptosis arising from inhibition of EGFR auto-phosphorylation and downstream silencing of associated signal transduction pathways. PR610 is optimized for long tumor residency (T½ >2 days); in a preclinical model of erlotinib-resistant NSCLC, a single injection of PR610 produces profound, global shutdown of signal transduction via EGFRT790M/L858R. Tumor PR610E concentrations were above cellular anti-proliferative IC50 concentrations for over 5 days, being more than sufficient to induce apoptosis via “oncogenic shock”. Pharmacokinetic (PK) studies of PR610 show significant differences in species toxicokinetics. Both the rat and dog preclinical toxicology models display considerable systemic conversion of PR610 to PR610E (6% - 30% and 24% - 29% of prodrug AUC, respectively) with attendant symptoms of EGFR inhibition including acneiform skin rash and diarrhea. In contrast NIH-III nude mice display minimal circulating TKI (PR610E) relative to PR610 (1.5% - 1.7% of AUC) consistent with a substantially improved tolerance as judged by PR610 plasma AUCinf at the maximum tolerated dose (MTD). Human subjects from the phase I clinical trial consistently experience the lowest systemic levels of PR610E (Mean 1.06% ± 0.69%; range 0.34% - 2.7%; n=20) across dose levels ranging from 10 - 150 mg/m2. Notably, a dose of 150 mg/m2 in human subjects produces a PR610 plasma AUCinf equivalent to that measured for 30 mg/kg PR610 in NIH-III mice, a dose that is active in several HER-dependent subcutaneous tumor xenograft models. Collectively, these data indicate that PR610 has the desirable characteristics of a deactivated prodrug in human subjects and preclinical models predict that an active dose range has been reached in the phase I trial. PR610 is a first-in-class hypoxia-selective EGFR/HER2 inhibitor with exciting clinical potential. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B278. Citation Format: Adam V. Patterson, Jagdish Jaiswal, Kendall Carlin, Maria R. Abbattista, Christopher P. Guise, Shevan Silva, Ho Lee, Guo-Liang Lu, Robert F. Anderson, Teresa J. Melink, John C. Gutheil, Jeff B. Smaill. PR610: A novel hypoxia-selective tyrosine kinase inhibitor in phase I clinical trial. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B278.

Hypoxia occurs in most human tumors and is associated with disease progression, treatment resistance and poor patient outcome. We have developed the hypoxia-activated prodrug SN29966, designed to release the irreversible pan-HER inhibitor SN29926, following one-electron reduction by hypoxic cells (Smaill et al, Mol Cancer Ther., 2009; 8(12 Suppl), C46). Pharmacokinetic (PK) studies in nude mice bearing A431 tumor xenografts indicated SN29966 has a long tumor half-life (>3 days) and releases SN29926 in tumors. SN29966 demonstrated single agent activity in nude mice bearing A431 and SKOV3 xenografts, inducing striking tumor regressions in both models (Patterson et al, Mol Cancer Ther., 2009; 8(12 Suppl), B76). PR509 and PR610, clinical candidates developed from SN29966, are currently undergoing comparative evaluation with Phase I trials anticipated in early 2012. The single-agent antitumor activity of SN29966 is arguably counter-intuitive given that it is designed to target hypoxic cells within tumors. This activity may arise from a number of contributing mechanisms including; (i) bioactivity of the unreduced prodrug; (ii) local redistribution of released inhibitor in the tumor; (iii) liver metabolism and circulating inhibitor and (iv) a long tumor half-life allowing for targeting of both chronic and cycling hypoxia. To critically assess the relative contribution of each to the mechanism of action of SN29966 we performed a number of studies. We prepared SN31950, a prodrug of SN29926 designed to be incapable of one-electron fragmentation. In target modulation and anti-proliferative assays SN31950 showed no hypoxia-dependent activity. The murine A431 tumor PK of SN29966 and SN31950 demonstrated that at an equimolar dose (20 μmol/kg, ip), both prodrugs gave comparable tumor exposures (AUC0–72h: SN31950, 50 μmol*h/kg; SN29966, 57 μmol*h/kg). In contrast, the tumor exposure of SN29926 released from each prodrug differed by 40-fold (AUC0–72h: SN29926 from SN31950, 0.3 μmol*h/kg; SN29926 from SN29966, 12 μmol*h/kg). Plasma exposure of each prodrug was comparable, as were levels of SN29926 in plasma (presumed mainly due to hepatic prodrug metabolism). Consistent with the observed lack of inhibitor release in A431 tumors, SN31950 was inactive against A431 tumors in growth delay assays. To confirm the hypoxia-dependent nature of SN29966 inhibitor release in A431 tumors we re-oxygenated tumors in mice breathing 100% oxygen at 2.5 atm in a hyperbaric chamber. Accordingly, mice showed a marked reduction (56%, p Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A247.

Reversible HER1 (EGFR) inhibitors erlotinib and gefitinib are approved for use in non-small cell lung cancer (NSCLC), particularly demonstrating activity against tumors expressing mutant forms of HER1. Unfortunately, relapse invariably occurs in this patient population, with approximately half of patients having acquired an additional T790M mutation in HER1. Irreversible pan-HER inhibitors (BIBW2992, PF00299804) are under clinical evaluation in the context of NSCLC that has relapsed post-erlotinib/gefitinib treatment. However it is currently unclear whether these agents possess the therapeutic index in man necessary to gain approval in this setting (Regales et al., J. Clin. Invest. 2009, 119:3000-10), prompting the development of HER1T790M mutant-selective irreversible inhibitors (Zhou et al., Nature. 2009, 462: 1070-74). Hypoxia occurs in most human tumors and is associated with disease progression, resistance to conventional therapies and poor patient outcome. It can however be considered as an exploitable physiological target, as it supports tumor-selective bioreduction of prodrugs. We have developed hypoxia-activated prodrugs of irreversible pan-HER inhibitors as a strategy to broaden their therapeutic index. SN29966 is a prototype nitromethylaryl quaternary (NMQ) ammonium salt prodrug of an irreversible pan-HER inhibitor (SN29926), with masked cellular activity. Radiolytic reduction of SN29966 demonstrated fragmentation of the one-electron adduct to release SN29926 [kfrag 130 ± 10 s-1], and hypoxia-selective metabolism to SN29926 has been confirmed in all cell lines tested. SN32807 is the lead prodrug of this series, releasing the irreversible pan-HER inhibitor SN32793 in a hypoxia-dependent manner. In a panel of HER1/HER1T790M/HER2-expressing cell lines SN32807 showed hypoxia-dependent inhibition of proliferation (hypoxic/oxic IC50 ratios of 60, 11 and 20 in A431, H1975 and SKOV3 cells, respectively), a property SN32793 lacked (IC50 ratios 0.8-1.6). Tumor growth delay experiments (NIH-III nude mice) in large (500 mm3) HER1T790M-expressing H1975 tumor xenografts showed BIBW2992 (20 mg/kg, p.o. daily) failed to control tumor growth (i.e. progressive disease), with only a modest Tumor Growth Delay value of 35% [TGD % = [(T-C)/C]x100 where T and C are time to 4-fold increase in tumor volume from treatment day-1 for treated and control tumors, respectively]. In contrast, single-agent SN32807 (88 mg/kg; ip, q3dx8) demonstrated complete tumor responses in all animals during the treatment period (TGD value 246%; P Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-297.