6-Substituted amiloride derivatives as inhibitors of the urokinase-type plasminogen activator for use in metastatic disease

The oral K+-sparing diuretic amiloride shows anti-cancer side-activities in multiple rodent models. These effects appear to arise, at least in part, through moderate inhibition of the urokinase-type plasminogen activator (uPA, K_i = 2.4 µM), a pro-metastatic trypsin-like serine protease that is upregulated in many aggressive solid malignancies. In applying the selective optimization of side-activity (SOSA) approach, a focused library of twenty two 6-substituted amiloride derivatives were prepared, with multiple examples displaying uPA inhibitory potencies in the nM range. X-ray co-crystal structures revealed that the potency increases relative to amiloride arise from increased occupancy of uPA's S1β subsite by the appended 6-substituents. Leading compounds were shown to have high selectivity over related trypsin-like serine proteases and no diuretic or anti-kaliuretic effects in rats. Compound 15 showed anti-metastatic effects in a xenografted mouse model of late-stage lung metastasis.

Screening of 5- and 6-Substituted Amiloride Libraries Identifies Dual-uPA/NHE1 Active and Single Target-Selective Inhibitors

The K⁺-sparing diuretic amiloride shows off-target anti-cancer effects in multiple rodent models. These effects arise from the inhibition of two distinct cancer targets: the trypsin-like serine protease urokinase-type plasminogen activator (uPA), a cell-surface mediator of matrix degradation and tumor cell invasiveness, and the sodium-hydrogen exchanger isoform-1 (NHE1), a central regulator of transmembrane pH that supports carcinogenic progression. In this study, we co-screened our library of 5- and 6-substituted amilorides against these two targets, aiming to identify single-target selective and dual-targeting inhibitors for use as complementary pharmacological probes. Closely related analogs substituted at the 6-position with pyrimidines were identified as dual-targeting (pyrimidine 24 uPA IC₅₀ = 175 nM, NHE1 IC₅₀ = 266 nM, uPA selectivity ratio = 1.5) and uPA-selective (methoxypyrimidine 26 uPA IC₅₀ = 86 nM, NHE1 IC₅₀ = 12,290 nM, uPA selectivity ratio = 143) inhibitors, while high NHE1 potency and selectivity was seen with 5-morpholino (29 NHE1 IC₅₀ = 129 nM, uPA IC₅₀ = 10,949 nM; NHE1 selectivity ratio = 85) and 5-(1,4-oxazepine) (30 NHE1 IC₅₀ = 85 nM, uPA IC₅₀ = 5715 nM; NHE1 selectivity ratio = 67) analogs. Together, these amilorides comprise a new toolkit of chemotype-matched, non-cytotoxic probes for dissecting the pharmacological effects of selective uPA and NHE1 inhibition versus dual-uPA/NHE1 inhibition.

Antibacterial properties of 3-(phenylsulfonyl)-2-pyrazinecarbonitrile

The emergence of multidrug-resistant bacterial strains has heightened the need for new antimicrobial agents based on novel chemical scaffolds that are able to circumvent current modes of resistance. We recently developed a whole-animal drug-screening methodology in pursuit of this goal and now report the discovery of 3-(phenylsulfonyl)-2-pyrazinecarbonitrile (PSPC) as a novel antibacterial effective against resistant nosocomial pathogens. The minimum inhibitory concentrations (MIC) of PSPC against Staphylococcus aureus and Enterococcus faecium were 4 μg/mL and 8 μg/mL, respectively, whereas the MICs were higher against the Gram-negative bacteria Klebsiella pneumoniae (64 μg/mL), Acinetobacter baumannii (32 μg/mL), Pseudomonas aeruginosa (>64 μg/mL), and Enterobacter spp. (>64 μg/mL). However, co-treatment of PSPC with the efflux pump inhibitor phenylalanine arginyl β-naphthylamide (PAβN) or with sub-inhibitory concentrations of the lipopeptide antibiotic polymyxin B reduced the MICs of PSPC against the Gram-negative strains by >4-fold. A sulfide analog of PSPC (PSPC-1S) showed no antibacterial activity, whereas the sulfoxide analog (PSPC-6S) showed identical activity as PSPC across all strains, confirming structure-dependent activity for PSPC and suggesting a target-based mechanism of action. PSPC displayed dose dependent toxicity to both Caenorhabditis elegans and HEK-293 mammalian cells, culminating with a survival rate of 16% (100 μg/mL) and 8.5% (64 μg/mL), respectively, at the maximum tested concentration. However, PSPC did not result in hemolysis of erythrocytes, even at a concentration of 64 μg/mL. Together these results support PSPC as a new chemotype suitable for further development of new antibiotics against Gram-positive and Gram-negative bacteria.

Structure-activity relationships of pyrazole-4-carbodithioates as antibacterials against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of serious hospital-acquired infections and is responsible for significant morbidity and mortality in residential care facilities. New agents against MRSA are needed to combat rising resistance to current antibiotics. We recently reported 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioate (HMPC) as a new bacteriostatic agent against MRSA that appears to act via a novel mechanism. Here, twenty nine analogs of HMPC were synthesized, their anti-MRSA structure-activity relationships evaluated and selectivity versus human HKC-8 cells determined. Minimum inhibitory concentrations (MIC) ranged from 0.5 to 64 μg/mL and up to 16-fold selectivity was achieved. The 4-carbodithioate function was found to be essential for activity but non-specific reactivity was ruled out as a contributor to antibacterial action. The study supports further work aimed at elucidating the molecular targets of this interesting new class of anti-MRSA agents.

Systematic evaluation of structure-property relationships and pharmacokinetics in 6-(hetero)aryl-substituted matched pair analogs of amiloride and 5-(N,N-hexamethylene)amiloride

The K+-sparing diuretic amiloride elicits anticancer activities in multiple animal models. During our recent medicinal chemistry campaign aiming to identify amiloride analogs with improved properties for potential use in cancer, we discovered novel 6-(hetero)aryl-substituted amiloride and 5-(N,N-hexamethylene)amiloride (HMA) analogs with up to 100-fold higher potencies than the parent compounds against urokinase plasminogen activator (uPA), one of amiloride's putative anticancer targets, and no diuretic or antikaliuretic effects. Here, we report the systematic evaluation of structure-property relationships (lipophilicity, aqueous solubility and in vitro metabolic stability in human and mouse liver microsomes) in twelve matched pair analogs selected from our 6-substituted amiloride and HMA libraries. Mouse plasma stability, plasma protein binding, Caco-2 cell permeability, cardiac ion channel activity and pharmacokinetics in mice (PO and IV) and rats (IV) are described alongside amiloride and HMA comparators for a subset of the four most promising matched-pair analogs. The findings combined with earlier uPA activity/selectivity and other data ultimately drove selection of two analogs (AA1-39 and AA1-41) that showed efficacy in separate mouse cancer metastasis studies.

Surgery for testicular cancer: indication, results and technical aspects

The standard therapeutique approach to patients with advanced germ cell tumors of the testis is a combination of systemic chemotherapy with surgical removal of the residual disease. The indication of surgery, residual tumor resection (RTR) or retroperitoneal lymph node dissection (RPLND), has changed during the last 10 years. Sugery is not longer recommended after chemotherapy of pure seminoma and surveillance of the residual tumor is the favored option. RPLND is a critical component of the treatment armentarium in low-stage nonseminomatous germ cell. RPLND is an accurate staging tool prviding important information to dtermine the need for chemotherapy. When performed properly, RPLND eliminates the retroperitoneum as a site for relapse, wich in turn provides emotional and psychological relief to the patient, and simplifies the follow-up protocol. In advanced nonseminomatous tumours, surgery after chemotherapy is recommended in most of the cases since large studies have shown that a considerable proportion of patients with complete radiological remission after chemotherapy harbor vital carcinoma or teratoma. Prediction models of necrosis after chemotherapy in order to avoid RTR are generally accepted since the accuracy of most models is too low. RTR is indicated in patients with elevated markers after two different chemotherapy regimens (including salvage chemotherapy) either to resect teratoma or cystic residual disease or to remove chemorefractory disease. Laparoscopic approache is a viable staging tool; however, oncologic control of the retroperitoneum has not been reliably determined.

Automated Patch Clamp Screening of Amiloride and 5-N,N-Hexamethyleneamiloride Analogs Identifies 6-Iodoamiloride as a Potent Acid-Sensing Ion Channel Inhibitor

Acid-sensing ion channels (ASICs) are transmembrane sensors of extracellular acidosis and potential drug targets in several disease indications, including neuropathic pain and cancer metastasis. The K⁺-sparing diuretic amiloride is a moderate nonspecific inhibitor of ASICs and has been widely used as a probe for elucidating ASIC function. In this work, we screened a library of 6-substituted and 5,6-disubstituted amiloride analogs using a custom-developed automated patch clamp protocol and identified 6-iodoamiloride as a potent ASIC1 inhibitor. Follow-up IC₅₀ determinations in tsA-201 cells confirmed higher ASIC1 inhibitory potency for 6-iodoamiloride 94 (hASIC1 94 IC₅₀ = 88 nM, cf. amiloride 11 IC₅₀ = 1.7 μM). A similar improvement in activity was observed in ASIC3-mediated currents from rat dorsal root ganglion neurons (rDRG single-concentration 94 IC₅₀ = 230 nM, cf. 11 IC₅₀ = 2.7 μM). 6-Iodoamiloride represents the amiloride analog of choice for studying the effects of ASIC inhibition on cell physiology.

Epoetin beta (NeoRecormon) corrects anaemia in patients with hormone-refractory prostate cancer and bone metastases

BACKGROUND

Severe anaemia is common in patients with metastatic, hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

We evaluated the efficacy of epoetin beta in correcting anaemia and maintaining haemoglobin (Hb) levels in this group of patients. Patients with HRPC, bone metastases and anaemia (Hb < 12 g/dl) were included. Epoetin beta, 30,000 IU per week in three divided doses, was administered subcutaneously, with iron supplementation when needed. If Hb increased by < 1 g/dl during the first 4 weeks of therapy the epoetin dose was increased (increments of 5,000 IU per dose) at fortnightly intervals to a maximum of 60,000 IU per week. Patients with haematopoietic response (Hb increase > or = 2 g/dl from baseline or Hb level > or = 12 g/dl without blood transfusions) went on to receive epoetin beta 10,000 IU once weekly for up to 24 weeks.

RESULTS

All 29 evaluable patients demonstrated a haematopoietic response to epoetin beta treatment. None of the patients required blood transfusions. All patients showed improvements in quality of life (assessed using the EORTC QLQ-C30 questionnaire). Hb levels were maintained for the remainder of the trial. Epoetin beta was very well tolerated.

CONCLUSION

Epoetin beta therapy resulted in a rapid and sustained improvement in Hb levels in patients with HRPC metastatic to bone.