Late and early C4d-positive acute rejection: Different clinico-histopathological subentities in renal transplantation

This study was performed to investigate the clinical and pathologic features of C4d-positive steroid-resistant acute rejection (AR) at different phases after renal transplantation. Fifty-six kidney allograft recipients with C4d-positive AR were divided into three groups, very early rejection (VER, occurring < or =14 days following transplantation, n=28), early rejection (ER, occurring 15-180 days following transplantation, n=5), and late rejection (LR, occurring >180 days following transplantation, n=23). Clinical and pathological features were evaluated. Significantly more patients in the ER and LR groups were associated with a reduction or withdrawal of immunosuppressants. More patients in the ER and LR groups experienced a significant (>3 g/l) decrease in serum albumin (80% ER, 91.3% LR, 7.1% VER, P<0.001) and a decrease in hemoglobin (>1 g/dl) (80, 100 vs 17.9%, P<0.001). Most VER patients reported a fever and had very rapid graft dysfunction requiring dialysis. Significantly more patients (87%) had interstitial fibrosis and tubular atrophy in the LR group compared with the other groups and 13% had transplant glomerulopathy. Most cases of VER were reversed with tacrolimus and mycophenolate mofetil treatment, with or without immunoadsorption, with a 1-year survival rate of 96.4%, compared with only 60 and 52.2% in the ER and LR groups. In conclusion, C4d-positive steroid-resistant AR at different time points is associated with unique clinico-histopathological manifestations requiring distinct treatment strategies. Late episodes are usually associated with significantly reduced serum albumin and hemoglobin levels and a poorer outcome. A more specialized treatment protocol should be established for these patients.

Effect of phospholipid composition on characterization of liposomes containing 9-nitrocamptothecin

9-Nitrocamptothecin (9-NC), a newly developed camptothecin derivative, had poor solubility in any pharmaceutically acceptable solvents. One way of improving the solubility is to formulate the drug into liposomes. However, 9-NC has low affinity to lipid membranes resulting in a very low drug-to-liposome entrapment. We developed a novel liposome-based 9-NC formulation which was composed of soybean phosphatidylcholine (SPC), hydrogenated soybean phosphatidylcholine (HSPC), and cholesterol. Compared with conventional liposomes composed of only SPC and cholesterol, 9-NC/lipid molar ratio increased from 1:72 to 1:18 while incorporation efficiency was still maintained about 80%. In addition, after 9-NC was encapsulated into novel liposomes, pharmacokinetic results revealed an increase in area under the plasma concentration-time curve (AUC) and a decrease in distribution volume of 9-NC following intravenous administration to rats. Increased stability in plasma may account for the improved pharmacokinetic behavior of the novel liposomes. Effect of HSPC/SPC molar ratio on characterization of the novel liposomes was also investigated. Except for drug/lipid molar ratio and encapsulation efficiency, HSPC/SPC molar ratio had only a little effect on other properties of novel liposomes. In conclusion, the study suggests that the novel liposomes can act as promising carriers for hydrophobic substances such as 9-NC.

Tissue- and bone cell-specific expression of bone sialoprotein is directed by a 9.0 kb promoter in transgenic mice

Bone sialoprotein (BSP) is a phosphorylated glycoprotein that is expressed almost exclusively in mineralizing connective tissues. In bone, expression of BSP correlates with the differentiation of osteoblasts and the onset of mineralization. To determine how the tissue- and differentiation-specific transcription of BSP is regulated, various lengths of promoter sequence were ligated to a luciferase reporter and stably transfected into a rat stromal bone marrow cell line, RBMC-D8 and undifferentiated C3H10T1/2 cells. Luciferase transcription of reporter constructs including 5.4 kb (mBSP5.4Luc) and 9.0 kb (mBSP9.0Luc) of the BSP promoter was strongly up-regulated in parallel with endogenous BSP mRNA in differentiating SBMCs, but not in C3H10T1/2 cells. In contrast, 0.1 kb and 1.4 kb BSP promoter constructs did not show selective expression. To determine tissue-specific expression in vivo, transgenic mice expressing reporter constructs for the 9.0 kb promoter and a 4.8 kb promoter lacking two upstream Cbfa1/Runx2 elements (mBSP9.0Luc and mBSP4.8Luc, respectively) were generated. Analysis of various tissues collected from 1-, 4-, 7-, 14-, and 42-day-old mice revealed extremely high levels of luciferase activity in calvaria, mandible, and tibia of the mBSP9.0Luc mice. In contrast, soft tissues showed negligible luciferase expression. Mice harboring the 4.8 kb transgene also showed selective luciferase expression but displayed a significantly lower activity in mineralized tissues. Northern hybridization of endogenous BSP mRNA and immunostaining of BSP in mBSP9.0Luc mice showed a temporo-spatial expression pattern consistent with the luciferase activity. These results indicate that regulatory elements within the 9.0 kb region of the promoter are required for strong, tissue- and differentiation-specific expression of BSP.

Long-term non-cancer mortality among 39,657 one-year testicular cancer survivors (TCSs)

4508

Background: Multiple reports address the incidence of second cancer (SC) and long-term morbidity in TCSs, yet few data analyze the impact of non-malignant late sequelae on mortality. Methods: 39,657 one-year TCSs were identified in 14 population-based cancer registries in North America and Europe, with 17,856, 13,084 and 6,298 men followed for 10, 20 and 30 years, respectively. Standardized mortality ratios (SMRs), comparing TCSs to the general population, were calculated for deaths due to all non-cancer causes (n = 2,942) and specific sites. Further, absolute mortality due to TC, non-TC SC and all non-cancer disorders was estimated. Results: The SMR for all non-malignant diseases combined was 0.99 (95% CI: 0.95–1.02), with a significant reduction of deaths due to circulatory diseases (SMR: 0.92, n = 1,117). However, following initial treatment with chemotherapy and radiotherapy, the SMR for circulatory diseases was significantly elevated (SMR: 1.76), with a non-significant 29% excess after chemotherapy alone. Mortality due to digestive diseases was significantly increased (SMR: 1.32, n = 222), including gastric and duodenal ulcers (SMR = 1.52; excess deaths were observed between 10 and 25 years after initial radiotherapy). For the first 20 years after TC diagnosis, deaths due to infection were significantly elevated (SMR: 1.52, n=211). Absolute mortality due to non-cancer disorders always exceeded that due to SC, and was 15% after 30 years in a TCS diagnosed at age 35 compared with about 11% for SC. Conclusions: Compared with the general population, the overall risk of mortality due to all non-cancer causes combined does not appear to be increased in TCSs. However, they experience excess non-cancer deaths due to infection and digestive diseases, but not circulatory diseases. Additional analytic studies with detailed data on treatment and co-morbidities are required to further evaluate associations with specific causes of death.

No significant financial relationships to disclose.

A pharmacokinetic study of Genetaxyl (G) together with cyclosporin A (CsA) administered orally in cancer patients

12002

Background: Oral administration of paclitaxel given with CsA has shown promising activity in Phase II trials, but the apparent bioavailability is low and dose-dependent due to the presence of high concentrations of Cremophor EL (CrEL). We hypothesized that the use of a novel oral paclitaxel formulation containing only 20% CrEL (Genetaxyl [G]; Genovate Biotechnology Ltd., Taiwan), given with CsA is associated with an improved pharmacokinetic (PK) profile. Methods: Cohorts of 6 patients with cancer were treated with oral G at a dose of 60, 120, or 180 mg/m2 and 10 mg/kg of oral CsA in cycle 1. In cycle 2, patients received IV G (175 mg/m2, 3-h infusion). Three additional patients received generic IV paclitaxel (GIP). Serial blood samples were analyzed by LC/MS/MS and equilibrium dialysis, to determine total and unbound paclitaxel PK. Results: The mean (± SD) total paclitaxel AUCs were 1299±189, 1682±636, and 2204±1407 ng.h/mL at the 3 consecutive dose levels, suggesting nonlinear PK. However, based on unbound AUC, the oral bioavailability was dose-independent (P=.62), with a mean value of 37.2±18.6% (n=15). As expected, the total paclitaxel AUC following IV G (9024±4648 ng·h/mL) was lower than that for IV GIP (13,732±3983 ng·h/mL), as a result of increased clearance (39.6 vs 18.3 L/h) and a larger volume of distribution (768 vs 268 L). Interestingly, the unbound paclitaxel AUC was similar between the two IV formulations (P=.25), as the ratio of unbound/total paclitaxel for G was 2.5 times higher than that for GIP (12.5 vs 4.9%). Toxicity profiles were mild, with only 2 patients experiencing ≥ Gr 3 myelosuppression following oral G at 180 mg/m2. Conclusions: The mean bioavailability of paclitaxel following oral Genetaxyl with CsA was about 37%, which is higher than that observed previously with paclitaxel (range, 21–31%). Further clinical exploration of oral Genetaxyl in taxane-sensitive diseases is warranted.

[Table: see text]

Screening a library of FDA-approved drugs identifies agents that induce lytic viral infection in EBV-associated tumors

2002

Background: Epstein-Barr virus (EBV) is associated with a variety of tumors including AIDS lymphoma, Burkitt’s lymphoma, nasopharyngeal carcinoma and Hodgkin’s lymphoma. We hypothesized that drugs used in practice might alter viral gene expression in tumor cells in ways that might be important to understand. For example induction of lytic viral gene expression leads to expression of immunodominant CD8 T cell antigens and expression of the viral thymidine kinase (which phosphorylates ganciclovir and other nucleotide analogues). Methods: A library of FDA-approved drugs that includes 2720 agents was screened to identify those that upregulated EBV lytic gene expression. The screen involved a Burkitt’s cell line with a recombinant GFP-EBV that assayed the impact of agents on replication of the complete viral genome, and assay of a lytic promoter reporter construct. Results: The assay identified 146 agents in the whole virus replication assay, 195 agents in the promoter assay, and 54 agents that were active in both assays. Agents with activity could be grouped into 4 families: anti-tubulin drugs, glucocorticoid and other steroid hormones, DNA damaging agents and nucleotide analogues (including cytarabine and gemcitabine), and the proteasome inhibitor bortezomib. Anti-tubulin drugs and nucleotide analogues were less active in thes whole virus assay than the promoter assay whereas bortezomib showed similar activity in both assays. Followup studies confirmed that bortezomib is a potent viral lytic activator that increases expression of the viral thymidine kinase and virion production in several different Burkitt’s lymphoma and primary effusion lymphoma cell lines. Although bortezomib decreases NFKB levels, in vitro investigations with an IKB repressor suggests that inhibition of NFKB alone does not account for lytic activation. Conclusions: Many cancer chemotherapeutic agents are upregulators of EBV lytic expression. Bortezomib is among the most potent. As strategies for using lytic induction therapeutically evolve, these agents may have an important role to play.

No significant financial relationships to disclose.

Gemcitabine, docetaxel, and capecitabine (GTX) in the treatment of metastatic pancreatic cancer (PC): A prospective phase II study

14024

Background: We have found that the combination of gemcitabine, docetaxel, and capecitabine (GTX), when administered in a specific sequence, will induce a p53 independent pathway of cell death through the MAP kinase pathway. The sequence overcomes drug resistance in PC cells in vitro. We have begun a prospective, phase II trial of GTX in patients with metastatic PC as first-line therapy. Methods: 23 patients with metastatic PC, ECOG 0–2 were enrolled at either Columbia or a community practice. Each cycle was administered over a 21 days. Capecitabine was administered at 750 mg/m2 twice daily for 14 days. Gemcitabine (750 mg/m2 over 75 minutes) and docetaxel (30 mg/m2) were administered on days 4 and 11. Responses were measured by CT (RECIST) and PET after every three cycles. A response by PET was defined as a 50% reduction in SUV while a CR was an absence of uptake. Results: Median age was 61, including 8 men and 15 women. Metastatic sites included liver (87%), abdomen (65%), and lung (17%). 70% of liver positive patients had at least five metastases. 22% had malignant ascites. 16 patients remain alive and 7 have progressive disease. Median survival has not yet been reached. Progression occurred at a median of 5.1 months. By CT, the response rate at metastatic sites was 39% (17% CR / 22% PR). Stable disease was observed in 48% at metastatic sites. PET showed a 53% response rate at metastatic sites. At the primary site, CT showed a 30% response rate including 17% complete responses. By PET criteria, there was a 31% response rate and a 26% CR rate at the primary site. In three patients, a PET response heralded a CT response by three cycles. In one patient, progressive disease on PET preceded progression on CT by two months. Toxicity: Grade 3 leukopenia and thrombocytopenia were 13% and 9%, respectively. There was no grade four hematologic toxicity. One patient experienced lung disease related to gemcitabine and withdrew from the study. A second patient experienced grade 4 mucositis, thrush, and sepsis which was presumed due to DPD deficiency. Grade 3–4 toxicities: HFS: 9%. There was no grade 3–4 diarrhea. Conclusions: GTX, elicits a promising response rate when used in metastatic P.C. PET detects a response and failure of chemotherapy earlier than CT scans.

[Table: see text]

Phase I study of pemetrexed plus cisplatin in unresectable, advanced gastric carcinoma in Taiwan

14009

Background: Phase I of this Phase I/II study (H3E-AA-S038) was conducted to determine the recommended dose of pemetrexed (PT) when given with cisplatin (Cis) to patients with unresectable, advanced gastric carcinoma. Methods: Patients 18 to 70 years of age, with stage IV disease or post-surgery recurrence, no prior palliative chemotherapy, and an ECOG performance status of 0 or 1 were included. Patients received PT and Cis on Day 1 every 21 days. Cis was dosed at 75 mg/m2. PT dosage was planned at 600, 700, 800, and 900 mg/m2. Vitamin B12 and folic acid supplementation, and dexamethasone (or equivalent corticosteroid) prophylaxis were required. The initial number of patients to be enrolled per dose level (DL) was 3. If 0/3 patients had dose-limiting toxicity (DLT), PT dose was escalated. If 1/3 patients had DLT, 3 more patients were enrolled at that DL. If ≥2 patients had DLT, the dose was not escalated further. The recommended dose of PT for Phase II was the highest dose at which <2/6 patients experienced DLT. The following toxicities were defined as DLT: death due to toxicity; neutropenia [<0/5 × 109/L for ≥5 days, or <1.0 × 109/L with fever (≥38.5 ºC)]; thrombocytopenia (<10.0 × 109/L, or <50.0 × 109/L with bleeding); AST or ALT >20 × ULN; and non-hematological toxicities of CTC grade 3 or 4 (except nausea and vomiting). Intra-patient dose escalation was not permitted. Results: Sixteen patients were enrolled. The mean (±SD) age of enrolled patients was 52.8 (±10.0) years, and the majority were male (62.5%). At DL1, 0/3 patients experienced DLT. At DL2, 1/6 patients had DLT. At DL3, 3/7 patients had DLT, and so PT dose was not escalated. All DLTs occurred in cycle 1; 2 involved neutropenia, 1 tumor hemorrhage, and 1 hypokalemia. Grade 3/4 toxicities were experienced by 12/16 (75%) patients, including 9 (56%) hematological and 10 (63%) non-hematological events. Five out of thirteen (38%) patients with measurable disease had a RECIST response (2 had a complete response, 1 each at DL1 and DL2; 3 had a partial response, 2 at DL2 and 1 at DL3). At this interim analysis, 2 patients were still on therapy. Conclusions: The recommended dose of PT is 700 mg/m2. Phase II will examine response and safety of PT plus Cis in advanced gastric carcinoma.

[Table: see text]

Randomized phase III trial of capecitabine/cisplatin (XP) vs. continuous infusion of 5-FU/cisplatin (FP) as first-line therapy in patients (pts) with advanced gastric cancer (AGC): Efficacy and safety results

LBA4018

Background: The oral fluoropyrimidine capecitabine has proven efficacy and safety in colorectal and breast cancer. Phase II data in AGC suggested that XP would show comparable efficacy to a standard FP regimen, with potential safety and convenience advantages. This phase III study evaluated XP vs. FP in first-line AGC. Methods: Pts with previously untreated measurable AGC received either oral capecitabine (1000mg/m2 bid d1–14) + cisplatin (80mg/m2 i.v. d1) q3w (XP arm) or 5-FU (800mg/m2/d continuous infusion, d1–5) + cisplatin (80mg/m2 i.v. d1) q3w (FP arm). XP requires 1 day per 3 weeks in hospital; FP requires 5 days. Pts were treated until disease progression or unacceptable toxicity. Primary endpoint: non-inferiority (NI) in progression-free survival (PFS), defined as upper limit of 95% CI of hazard ratio (HR) <1.4 (first test) and <1.25 (second test). Results: From Apr 03 to Jan 05, 316 pts were enrolled in 46 centers/13 countries. Arms were well balanced: median age (years, range) XP (56, 26–74), FP (56, 22–73); median Karnofsky PS 80 (range 70–100) in both arms; male/female (%): XP (64/36) FP (69/31). Median no. of cycles was 5 (XP and FP). Median follow-up is 22.1 months. Primary endpoint was met: HR 0.81 (95% CI 0.63–1.04). XP was superior to FP in terms of overall response rate (ORR, RECIST). Efficacy is presented in the table. Most common treatment-related grade 3/4 adverse events (XP vs. FP) were: neutropenia (16 vs. 19%), vomiting (7 vs. 9%), stomatitis (2 vs. 7%), diarrhea (5 vs. 5%), and anemia (5 vs. 3%). Other grade 3/4 events occurred in <5% of pts. The rate of all-grade hand-foot syndrome was low (22 vs. 4%). Conclusions: XP showed highly significant non-inferiority for PFS and significant superiority for ORR vs. FP with similar safety. These findings suggest that capecitabine should become the fluoropyrimidine of choice for AGC, given the efficacy, reduced hospitalization time and simplified regimen.

No significant financial relationships to disclose.

[Table: see text]

Phase II trial of a 2-hour infusion of gemcitabine plus carboplatin as first-line chemotherapy for advanced non-small cell lung cancer

17099

Background: Prolonged infusion of gemcitabine have shown increased levels of the active triphosphate metabolite that theorically could increase the response rate and toxicity. The objectives of this study were to evaluated the efficacy and safety of this combination of using gemcitabine as a rate infusion of 10 mg/m2 per min with carboplatin in front-line chemonaive patients with advanced NSCLC. Methods: Fifty-four chemonaive patients have been included. 44 were male and 10 female. Median age was 63 years (19–75). 13% had ECOG 0 and 53.7% ECOG 1 and 33.3% ECOG 2. 32 (59.2%) patients had adenocarcinoma, 13 (24.1%) squamous cell, 1 (1.9%) large cell carcinoma, and 8 (14.8%) others. Eight (14.8%) had stage IIIB and 46 (85.2%) stage IV. Treatment was consisted of 1200 mg/m2 gemcitabine given as a 2-hour continuous infusion (10 mg/m2 per min) on days 1 and 8 of each cycle an AUC 5 carboplatin as on day 1, repeating each cycle every 21 days. A total of 223 chemotherapy cycles were administered, with a median of 4 cycles per patient (range 1–6), and 15 (27.8%) patients received all six cycles. Results: Of the fifty-four patients enrolled, all were evaluated for toxicity (according to the WHO scale) and 51 assessed for response (according to the RECIST criteria), the overall response rate (ORR) was 41.2% (95% confidence interval, 28% to 57%), including two complete responses (CRs: 3.9%) and 19 partial responses (PRs: 37.3%). As per the intent-to-treat (ITT) analysis, the ORR was 38.9%. With a median follow-up time of 10.8 months, the median TTP was 5.0 months (range 3.7–6.3 months), median OS time was 11.5 months (range 9.9–13.1 months) and 1-year survival was 41.7% (95% CI 26% to 57%) and 2-year survival was 19.3% (4.4% to 34.2%).The main grade 3–4 toxicity consisted of neutropenia (55.6%) and thrombocytopenia (57.4%).Patients were required platelet transfusion in 27 cycles (12.1%) and haematopoietic growth factors support care in 56 (25.1%) cycles. No bleeding episodes were recorded. Grade 3 nausea/vomiting occurred in 5.6% and grade 1–2 skin rash occurred in 42.6%. Conclusions: Prolonged gemcitabine infusion combined with carboplatin is manageable tolerated and its efficacy is similar to that of other chemotherapeutic schemes used for NSCLC treatment.

No significant financial relationships to disclose.

The carbonic anhydrase I locus contains a c-Myb target promoter and modulates differentiation of murine erythroleukemia cells

The Myb proto-oncogene encodes a transcription factor (c-Myb) that is essential for normal hematopoiesis and is thought to regulate hematopoietic cell proliferation and differentiation by regulating expression of specific target genes. We identify the mouse erythroid-specific carbonic anhydrase I promoter (CAIe) as a target of c-Myb activity and demonstrate that Myb activity is critical for carbonic anhydrase I (CAI) expression in C19 MEL cells. CAI expression is downregulated when MEL cells differentiate in response to MEnT or treatment with N, N-hexamethylene bisacetamide (HMBA). Coexpression of GATA-1 with c-Myb results in synergistic activation of transcription from the CAIe promoter and both transcription factors interact with the CAIe promoter in vivo. We identify a novel 20 bp sequence in the CAIe promoter that is sufficient to mediate synergistic activation of the CAIe promoter by c-Myb and GATA-1. c-Myb and GATA-1 interact with this DNA sequence suggesting that c-Myb and GATA-1 may be contained in a complex that interacts with this region of the CAIe promoter. Forced expression of CAI delayed HMBA-induced differentiation of MEL cells and maintained them in a proliferating state. These data strongly suggest that CAI is a c-Myb target and is involved in regulating MEL cell proliferation and differentiation.

Narcissus symptomless virus: a new carlavirus of daffodils

A filamentous virus, with particles 600-650 nm long, was purified from Narcissus pseudonarcissus (daffodil) in Hangzhou and an antiserum prepared. After mechanical inoculation, the virus could be detected serologically in Narcissus species but not in some commonly used virus indicators. Infection was symptomless. The complete sequence of the genomic RNA (8281 nt) showed six predicted ORFs typical of carlaviruses. Pairwise comparisons of gene sequences and phylogenetic analysis demonstrated that the new virus should be classified as a carlavirus but that it was not closely related to members of any current species. We propose the name Narcissus symptomless virus (NSV).

Sexual dysfunction in women partners of men with erectile dysfunction

We evaluated 113 female partners of men with erectile dysfunction (ED) attending a sexual dysfunction clinic in order to define sexual dysfunction among these women. In all, 51 (45%) women denied having any sexual dysfunction. The other 62 (55%) responded to questions classifying their complaint(s) according to the international classification of female sexual dysfunction (FSD) in the following topics (40/62, 65%, reported having more than one problem): decreased sexual desire (n=35, 56%), sexual aversion (none), arousal (n=23, 37%) and orgasmic disorders (n=39, 63%), dyspareunia (n=19, 31%), vaginismus (n=3, 5%), and noncoital sexual pain (none). Many female partners of men with ED report having some form of sexual disorder, mostly orgasmic problems and decreased sexual desire. Therefore, for optimal outcome of ED treatment, evaluation and treatment of male and FSD should be addressed as one unit within the context of the couple, and be incorporated into one clinic of sexual medicine.

Parallel gene expressions of IL-6 and BNP during cardiac hypertrophy complicated with diastolic dysfunction in spontaneously hypertensive rats

There is increasing evidence showing that inflammation is involved in heart failure. However, heart failure may differ greatly due to different aetiologies. The role of inflammation in hypertensive heart failure, particularly in the early stage of cardiac dysfunction, has not been studied completely. This study aims at finding out whether inflammation is involved in the early stage of heart dysfunction due to hypertension.

METHODS

Ten spontaneously hypertensive rats (SHR) and ten age-matched Wistar rats were used. Cardiac morphology and function, as well as coronary flow reserve, were examined by echocardiography. mRNAs for cytokines and brain natriuretic peptide were determined by RT-PCR.

RESULTS

The results demonstrate cardiac hypertrophy with increased heart/body weight ratio in SHR. Echocardiographic examination has shown that SHR developed diastolic heart dysfunction as determined by tissue Doppler without decrease in systolic function. In heart biopsies, there were increased mRNA levels for interleukin-6 and brain natriuretic peptide whereas decreased mRNA for interleukin-2, beta adrenergic receptor, interferon and NFkb in SHR as compared to WKY group. Coronary flow remained unchanged in both groups.

CONCLUSION

SHR developed cardiac hypertrophy complicated with diastolic heart dysfunction with increased expression of brain natriuretic peptide, down-regulation of beta adrenergic receptors and simultaneous up-regulation of IL-6, which indicates active proinflammatory process as, at least partly, underlying mechanism during the early stage when cardiac hypertrophy associated with diastolic dysfunction occurs.

Bimatoprost: A Novel Antiglaucoma Agent

The aim of glaucoma therapy is to preserve vision by reducing intraocular pressure (IOP). Following recent National Eye Institute sponsored studies, it is becoming increasingly apparent that every mmHg of extra IOP lowering counts. Bimatoprost is the newest and most effective addition to the physician's armamentarium of ocular hypotensive drugs. Direct clinical comparisons have demonstrated that it is more efficacious than the prostaglandin (PG) FP receptor agonist prodrugs, latanoprost and travoprost, as well as a beta-adrenoceptor antagonist, timolol, alone or in fixed combination with the carbonic anhydrase inhibitor, dorzolamide. Moreover, patients that are refractory to latanoprost therapy may be successfully treated with bimatoprost. Such evidence provides support, at the clinical level, for the contention that bimatoprost is pharmacologically distinct from PG FP receptor agonist prodrugs. Bimatoprost is a structural analog of PGF2alpha-ethanolamide (prostamide F2alpha), which is formed from the endocannabinoid anandamide by a biosynthetic pathway involving cyclooxygenase-2 (COX-2). Their pharmacology is remarkably similar, such that bimatoprost may be regarded as a prostamide mimetic. The target receptor for bimatoprost and the prostamides appears unique and unrelated to PG- and endocannabinoid-sensitive receptors. Extensive ocular distribution/metabolism studies in non-human primates demonstrate that bimatoprost is not a prodrug, it remains essentially intact. Its profound ocular hypotensive effects may, therefore, be attributed to its prostamide-mimetic properties.