A phase II study of retifanlimab (INCMGA00012) in patients with squamous carcinoma of the anal canal who have progressed following platinum-based chemotherapy (POD1UM-202).

BACKGROUND: Locally advanced or metastatic squamous carcinoma of the anal canal (SCAC) has poor prognosis following platinum-based chemotherapy. Retifanlimab (INCMGA00012), a humanized monoclonal antibody targeting programmed death protein-1 (PD-1), demonstrated clinical activity across a range of solid tumors in clinical trials. We present results from POD1UM-202 (NCT03597295), an open-label, single-arm, multicenter, phase II study evaluating retifanlimab in patients with previously treated advanced or metastatic SCAC. PATIENTS AND METHODS: Patients ≥18 years of age had measurable disease and had progressed following, or were ineligible for, platinum-based therapy. Retifanlimab 500 mg was administered intravenously every 4 weeks. The primary endpoint was overall response rate (ORR) by independent central review. Secondary endpoints were duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. RESULTS: Overall, 94 patients were enrolled. At a median follow-up of 7.1 months (range, 0.9-19.4 months), ORR was 13.8% [95% confidence interval (CI) 7.6% to 22.5%], with one complete response (1.1%) and 12 partial responses (12.8%). Responses were observed regardless of human immunodeficiency virus or human papillomavirus status, programmed death ligand 1 (PD-L1) expression, or liver metastases. Stable disease was observed in 33 patients (35.1%) for a DCR of 48.9% (95% CI 38.5% to 59.5%). Median DOR was 9.5 months (range, 5.6 months-not estimable). Median (95% CI) PFS and OS were 2.3 (1.9-3.6) and 10.1 (7.9-not estimable) months, respectively. Retifanlimab safety in this population was consistent with previous experience for the PD-(L)1 inhibitor class. CONCLUSIONS: Retifanlimab demonstrated clinically meaningful and durable antitumor activity, and an acceptable safety profile in patients with previously treated locally advanced or metastatic SCAC who have progressed on or are intolerant to platinum-based chemotherapy.

Severity and 1-month outcome of SARS-CoV-2 infection in patients with solid cancers: a Danish nationwide cohort study.

BACKGROUND: Cancer patients are vulnerable to infections, are older and often have comorbidities in comparison to the general population, which increases the risk for severe outcomes related to COVID-19 diagnosis. METHODS: This study is a prospective, nationwide study in patients with solid cancer and SARS-CoV-2 infection included between 10 March to 15 June 2020. Patient's baseline characteristics were collected. The study's primary outcome was overall survival within 30 days of verified SARS-CoV-2 infection. Secondary outcomes were hospital admission, admission to an ICU, and need for supplemental oxygen. RESULTS: A total of 112 patients with a cancer diagnosis and verified SARS-CoV-2 infection were identified. After one month of follow up, hospitalization was required for 54% (n = 61) and 21% of the patients had died and 14 of the 23 deceased cancer patients were ≥70 years. Most patients were classified with mild COVID-19 symptoms (66%, n = 74); however, 48% (n = 23) of the ≥70-year-olds patients were classified with severe or critical COVID-19 symptoms. Among the total study population, 61% (n = 68) had comorbidities and comorbidity were more frequently observed among the deceased (91%, n = 21) and older cancer patients (≥70 years, 81%, n = 39). CONCLUSIONS: Acknowledging the low sample size in this study, our work shows that age and comorbidities, but not recent cytotoxic therapy, are associated with adverse outcomes of SARS-CoV-2 infection for patients with solid cancer. Particularly, patients with progressive disease seem to be at greater risk of a fatal outcome from COVID-19.HighlightsAge, performance status, and comorbidities are strong predictors of adverse outcome in cancer patients with SARS-CoV-2 infection.Patients with progressive cancer disease seem to be at greater risk of a fatal outcome from COVID-19.Recent cytotoxic therapy, however, did not seem to be associated with increased risk for adverse outcomes of SARS-CoV-2 infection for patients with solid cancer.

Monitoring the effect of first line treatment in RAS/RAF mutated metastatic colorectal cancer by serial analysis of tumor specific DNA in plasma.

BACKGROUND: Precision medicine calls for an early indicator of treatment efficiency. Circulating tumor DNA (ctDNA) is a promising marker in this setting. Our prospective study explored the association between disease development and change of ctDNA during first line chemotherapy in patients with RAS/RAF mutated metastatic colorectal cancer (mCRC). METHODS: The study included 138 patients with mCRC receiving standard first line treatment. In patients with RAS/RAF mutated tumor DNA the same mutation was quantified in the plasma using droplet digital PCR. The fractional abundance of ctDNA was assessed in plasma before treatment start and at every treatment cycle until radiologically defined progressive disease. RESULTS: RAS/RAF mutations were detected in the plasma from 77 patients. Twenty patients progressed on treatment and 57 stopped treatment without progression. The presence of mutated DNA in plasma was correlated with poor overall survival. A low level of ctDNA after the first cycle of chemotherapy was associated with a low risk of progression. On the other hand, a significant increase of ctDNA at any time during the treatment course was associated with a high risk of progression on continuous treatment. The first increase in ctDNA level occurred at a median of 51 days before radiologically confirmed progression. CONCLUSIONS: The results indicate that the ctDNA level holds potential as a clinically valuable marker in first line treatment of mCRC. A rapid decrease was associated with a prolonged progression free interval, whereas a significant increase gave notice of early progression with a relevant lead time.

Prognostic significance of circulating intact and cleaved forms of urokinase plasminogen activator receptor in inoperable chemotherapy treated cholangiocarcinoma patients.

BACKGROUND: High levels of intact and cleaved forms of the urokinase-type plasminogen activator receptor (uPAR) in both tissue and blood are associated with poor survival in several cancer diseases. The prognostic significance of uPAR in cholangiocarcinoma is unknown. The aims of this study were to determine if pre-treatment serum levels of uPAR forms and a decrease in levels during chemotherapy are predictive of survival in patients with inoperable cholangiocarcinoma. DESIGN AND METHODS: Patients with inoperable cholangiocarcinoma were consecutively included in the training set (n=108). A test set included patients from a different hospital using similar treatment guidelines (n=60). Serum levels of the different uPAR forms were determined using time-resolved fluorescence immunoassays (TR-FIA). The Cox proportional hazards model was used for the uni- and multivariate survival analyses. RESULTS: Baseline level of uPAR(I-III)+uPAR(II-III) was an independent predictor of survival (HR=2.08, 95% CI:1.46-2.97, p<0.0001). Applying the linear predictor from the training set to the test set, it was validated that uPAR(I-III)+uPAR(II-III) predicted overall survival (p=0.049). A high level of uPAR(I-III)+uPAR(II-III) after 2cycles of chemotherapy was associated with poor survival (HR=1.79, 95% CI:1.08-2.97, p=0.023, n=57). This predictor, however, was not significant in the test set (p=0.21, 26 events in 27 patients). CONCLUSION: The baseline level of uPAR(I-III)+uPAR(II-III) is a predictor of survival in inoperable cholangiocarcinoma patients.

Phase II marker-driven trial of panitumumab and chemotherapy in KRAS wild-type biliary tract cancer.

BACKGROUND: Combination chemotherapy has proven beneficial in biliary tract cancer and further improvements may be achieved by individualizing treatment based on biomarkers and by adding biological agents. We report the effect of chemotherapy with panitumumab as first-line therapy for KRAS wild-type irresectable biliary tract cancer. PATIENTS AND METHODS: Patients were treated with gemcitabine 1000 mg/m(2), oxaliplatin 60 mg/m(2), and panitumumab 6 mg/kg i.v. every 2 weeks followed by two daily administrations of capecitabine 1000 mg/m(2) in 7 days. RESULTS: During 22 months, 46 patients were included in a single institution. The primary end point, fraction of progression-free survival (PFS) at 6 months, was 31/42 [74%; 95% confidence interval (CI) 58% to 84%]. Forty-two patients had measurable disease. Response rate was 33% and disease control rate 86%. Median PFS was 8.3 months (95% CI 6.7-8.7 months) and median overall survival was 10.0 months (95% CI 7.4-12.7 months). Toxicity was manageable including eight cases of epidermal growth factor receptor-related skin adverse events of grade 2 or more. CONCLUSIONS: Marker-driven patient selection is feasible in the systemic treatment of biliary tract cancer. Combination chemotherapy with panitumumab in patients with KRAS wild-type tumors met the efficacy criteria for future testing in a randomized trial.

The relationship between serum vascular endothelial growth factor A and microsatellite instability in colorectal cancer.

AIM: It has been suggested that colorectal neoplasms with or without microsatellite instability (MSI) can stimulate angiogenesis in different ways. The vascular endothelial growth factor (VEGF) system is essential for the angiogenetic process and the growth of malignant tumours. The aim of this study was to analyse the relationship between serum VEGF-A and the MSI status of patients with colorectal cancer (CRC). METHOD: In the study, 249 patients with CRC were divided into a test cohort of 83 patients and a validation cohort of 166. MSI was determined using immunohistochemistry. Tumours lacking protein expression of any of the four mismatch repair genes (MLH1, PMS2, MSH2 or MSH6) were labelled as high MSI. The rest were considered to be microsatellite stable (MSS). The serum VEGF-A analyses were performed by ELISA. RESULTS: The tumours of 15 patients in the test cohort and 27 in the validation cohort were classified as MSI. In the test cohort, patients with an MSI tumour had a significantly higher median serum VEGF-A concentration [617 pg/ml (95% CI 445-863)], compared with patients with an MSS tumour, [317 pg/ml (95% CI 224-386)], P = 0.01. A similar relationship was confirmed in the validation cohort, P = 0.04. CONCLUSION: This study provides some evidence to suggest that patients with an MSI tumour have higher serum VEGF-A levels than patients with an MSS tumour. If further validated, these findings could be of importance when considering the effects of anti-VEGF-A treatment.

EGF61A>G polymorphism as predictive marker of clinical outcome to first-line capecitabine and oxaliplatin in metastatic colorectal cancer.

BACKGROUND: The purpose of the present study was to investigate polymorphisms related to the metabolism of fluoropyrimidine and oxaliplatin, thymidylate synthase (TS) and excision repair cross-complementing gene 1 (ERCC1) 118, in metastatic colorectal cancer patients treated with capecitabine and oxaliplatin (XELOX). We also investigated the importance of the EGF61A>G polymorphism, which holds a functional influence on the tyrosine kinase receptor regulation. MATERIALS AND METHODS: We included 68 patients treated with first-line XELOX. Polymorphism analyses were carried out on pretreatment blood samples. Response was evaluated according to the RECIST. Survival analysis was described by the Kaplan-Meier method and log-rank testing. RESULTS: The overall response rate was 38% and the median overall survival 19.4 months. A favorable outcome was seen in patients with the EGF61A/G genotype compared with the combined group of A/A and G/G, with response rates of 57% and 18%, respectively (P = 0.001). There was a significantly different progression-free survival (P = 0.018) in favor of the A/G group. The TS and ERCC1 genotypes failed to provide any significant impact on the outcome. CONCLUSION: Polymorphism analysis of a simple blood sample is a feasible approach to biomarker analysis and the EGF61A>G polymorphism may influence the effect of first-line XELOX. Consequently, this marker deserves further investigation.

Clinical outcome in 520 consecutive Danish rectal cancer patients treated with short course preoperative radiotherapy.

AIM: The purpose of this study was to analyse the results of preoperative short course radiotherapy in a consecutive, national cohort of patients with rectal cancer. METHODS: Through a validated, prospective national database we identified 520 Danish patients who presented with high-risk mobile tumours in the lower two thirds of the rectum and were referred for preoperative radiotherapy with 5 x 5 Gy. The inclusion period was 56 months. Radiotherapy data was retrospectively collected. RESULTS: Of the 520 patients, 514 completed radiotherapy and 506 had surgery. Surgery was considered curative in 439 patients. The 3-year local recurrence rate was 4.0% (95% CI 2.5-6.5%) and the distant recurrence rate at 3 years was 18.7% (95% CI 15.4-22.5%). The 5-year disease free survival rate was 40.2% (95% CI 27.0-53.1%) and overall survival 50.4% (95% CI 36.1-63.1%). Most tumours (61%) were classified as T3 or T4 and 41% of the local recurrences occurred in patients with a fixed tumour at surgery. CONCLUSION: This study confirms data from randomised studies that the short course 5 x 5 Gy regime is a feasible treatment for locally advanced rectal cancer even when applied in a population outside clinical trials.

A national cohort study of long-course preoperative radiotherapy in primary fixed rectal cancer in Denmark.

OBJECTIVE: Preoperative radiotherapy has been shown to enable a fixed rectal cancer to become resectable which in turn may result in long-time survival. In this study, we analysed the outcome of long-course preoperative radiotherapy in fixed rectal cancer in a national cohort including all Danish patients registered with primary inoperable rectal cancer and treated in the period May 2001 to December 2005. METHOD: The study was based on surgical and demographic data from a continuously updated and validated national database. In addition, retrospective data were retrieved from all departments of radiotherapy concerning technique of radiotherapy, dose and fractionation and use of concomitant chemotherapy. Outcome was determined by actuarial analysis of local control, disease-free survival and overall survival. RESULTS: A total of 258 patients with fixed rectal cancer received long-course radiotherapy (> 45 Gy). The median age at diagnosis was 66 years (range: 32-85) and 185 (72%) patients were male. The resectability rate was 80%, and a R0 resection was obtained in 148 patients (57% of all patients and 61% of those operated). The 5-year local recurrence rate for all patients was 5% (95% CI: 3-7%), and the actuarial distant recurrence rate was 41% (95% CI: 35-47%). The cumulative 5-year disease-free survival was 27% (95% CI: 22-32%) and overall 5-year survival was 34% (95% CI: 29-39%). CONCLUSIONS: This study is the first population-based report on outcome of preoperative long-course radiotherapy in a large unselected patient group with clinically fixed rectal cancer. Most patients could be resected with the intention of cure and one in three was alive after 5 years.

Strategy in clinical practice for classification of unselected colorectal tumours based on mismatch repair deficiency.

OBJECTIVE: Deficiency of DNA mismatch repair (MMR) causes microsatellite instability (MSI) in a subset of colorectal cancers. Patients with these tumours have a better prognosis and may have an altered response to chemotherapy. Some of the tumours are caused by hereditary mutations (hereditary nonpolyposis colon cancer or Lynch syndrome), but most are epigenetic changes of sporadic origin. The aim of this study was to define a robust and inexpensive strategy for such classification in clinical practice. METHOD: Tumours and blood samples from 262 successive patients with colorectal adenocarcinomas were collected. Expression of the MMR proteins MLH1, MSH2, and MSH6 by immunohistochemistry (IHC) was compared with MSI DNA analysis. Methylation analysis of MLH1 and mutation analysis for BRAF V600E were compared in samples with MSI and/or lack of MLH1 expression to determine if the tumour was likely to be sporadic. RESULTS: Thirty-nine (14.9%) of the tumours showed MMR deficiency by IHC or by microsatellite analysis. Sporadic inactivation by methylation of MLH1 promoter was found in 35 patients whereby the BRAF activating V600E mutation, indicating sporadic origin, was found in 32 tumours. On the basis of molecular characteristics we found 223 patients with intact MMR, 35 patients with sporadic MMR deficiency, and four patients who were likely to have hereditary MMR deficiency. CONCLUSION: To obtain the maximal benefit for patients and clinicians, MMR testing should be supplemented with MLH1 methylation or BRAF mutation analysis to distinguish sporadic patients from likely hereditary ones. MMR deficient patients with sporadic disease can be reassured of the better prognosis and the likely hereditary cases should receive genetic counselling.

Pharmacokinetic profiles of biphasic insulin aspart 30/70 and 70/30 in patients with Type 1 diabetes: a randomized double-blinded crossover study.

AIMS: To compare pharmacokinetic characteristics of two biphasic insulin aspart (BIAsp) formulations: BIAsp30 and BIAsp70 (30% and 70%, respectively, of fast-acting insulin aspart) during 15 days of multiple dosing (thrice daily). METHODS: A total of 22 patients with Type 1 diabetes (nine women, 13 men) aged 41.4 +/- 9.9 years (mean +/- sd) with a diabetes duration of 18.9 (2.3-40.3) years (median and range) completed the randomized, double-blinded, two-period crossover study. On day 1 and day 15 of each treatment period, 24-h serum insulin and glucose profiles were evaluated. Total area under the insulin aspart concentration-time curve (AUC(0-24 h)), AUC after dinner administration stratified into early (AUCdinner(0-6 h)) and intermediate-phase (AUCdinner(6-14 h)), maximum insulin concentration (Cmax), time to maximum insulin concentration (Tmax) after each meal were recorded. RESULTS: On day 15 BIAsp70 was associated with a shorter Tmax, and more than 40% elevated Cmax. Comparing with BIAsp30, AUC(0-24 h) and AUCdinner(0-6 h) were increased by 25% and 28%, respectively, but AUCdinner (6-14 h) was markedly lower for BIAsp70 [BIAsp30/BIAsp70: 1.9; 95% CI (1.42, 2.55)]. Similar findings were also observed on day 1. The fasting or pre-meal serum insulin levels on day 15 tended to be higher with BIAsp30, but the differences were not statistically significant. CONCLUSIONS The pharmacokinetic properties of BIAsp30 and 70 remain constant during 2 weeks of daily administration in patients with Type 1 diabetes. In comparison with BIAsp30, the administration of BIAsp70 results in a shorter time to and larger maximum insulin aspart concentration. Furthermore, total and early post-dinner insulin AUC were greater, whereas late-phase insulin exposure was lower with BIAsp70.

Linker length in podophyllotoxin-acridine conjugates determines potency in vivo and in vitro as well as specificity against MDR cell lines.

We have synthesized two podophyllotoxin-acridine conjugates-pACR6 and pACR8. In these compounds an 9-acridinyl moiety is beta linked to the C4 carbon of the four ring system in 4'-demethylepipodophyllotoxin (epiDPT) via eighter an N-6-aminohexanylamide linker (pACR6) or via an N-8-aminooctanylamide linker containing two more carbon atoms (pACR8). The acridine-linker moiety occupies the position where different glucoside moieties, dispensable for activity, are normally linked to epiDPT in the well known epipodophyllotoxins VP-16 and VM-26. As with VP-16 and VM-26, pACR6 and pACR8 show evidence of being topoisomerase II poisons as they stimulate topoisomerase II mediated DNA cleavage in vitro and induce DNA damage in vivo. This in vivo DNA damage, as well as pACR6/pACR8 mediated cytotoxicity, is antagonized by the catalytic topoisomerase II inhibitors ICRF-187 and aclarubicin, demonstrating that topoisomerase II is a functional biological target for these drugs. Despite their structural similarities, pACR6 was more potent than pACR8 in stimulating topoisomerase II mediated DNA cleavage in vitro as well as DNA damage in vivo and pACR6 was accordingly more cytotoxic towards various human and murine cell lines than pACR8. Further, marked cross-resistance to pACR6 was seen among a panel of multidrug-resistant (MDR) cell lines over-expressing the MDR1 (multidrug resistance protein 1) ABC drug transporter, while these cell lines remained sensitive towards pACR8. pACR8 was also capable of circumventing drug resistance among at-MDR (altered topoisomerase II MDR) cell lines not over-expressing drug transporters, while pACR6 was not. Two resistant cell lines, OC-NYH/pACR6 and OC-NYH/pACR8, were developed by exposure of small cell lung cancer (SCLC) OC-NYH cells to gradually increasing concentrations of pACR6 and pACR8, respectively. Here, OC-NYH/pACR6 cells were found to over-express MDR1 and, accordingly, displayed active transport of 3H-labeled vincristine, while OC-NYH/pACR8 cells did not, further suggesting that pACR6, but not pACR8, is a substrate for MDR1. Our results show that the spatial orientation of podophyllotoxin and acridine moieties in hybrid molecules determine target interaction as well as substrate specificity in active drug transport.

N-terminal and core-domain random mutations in human topoisomerase II alpha conferring bisdioxopiperazine resistance.

Random mutagenesis of human topoisomerase II alpha cDNA followed by functional expression in yeast cells lacking endogenous topoisomerase II activity in the presence of ICRF-187, identified five functional mutations conferring cellular bisdioxopiperazine resistance. The mutations L169F, G551S, P592L, D645N, and T996L confer > 37, 37, 18, 14, and 19 fold resistance towards ICRF-187 in a 24 h clonogenic assay, respectively. Purified recombinant L169F protein is highly resistant towards catalytic inhibition by ICRF-187 in vitro while G551S, D645N, and T996L proteins are not. This demonstrates that cellular bisdioxopiperazine resistance can result from at least two classes of mutations in topoisomerase II; one class renders the protein non-responsive to bisdioxopiperazine compounds, while an other class does not appear to affect the catalytic sensitivity towards these drugs. In addition, our results indicate that different protein domains are involved in mediating the effect of bisdioxopiperazine compounds.

A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines.

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

Human small cell lung cancer NYH cells selected for resistance to the bisdioxopiperazine topoisomerase II catalytic inhibitor ICRF-187 demonstrate a functional R162Q mutation in the Walker A consensus ATP binding domain of the alpha isoform.

Bisdioxopiperazine drugs such as ICRF-187 are catalytic inhibitors of DNA topoisomerase II, with at least two effects on the enzyme: namely, locking it in a closed-clamp form and inhibiting its ATPase activity. This is in contrast to topoisomerase II poisons as etoposide and amsacrine (m-AMSA), which act by stabilizing enzyme-DNA-drug complexes at a stage in which the DNA gate strand is cleaved and the protein is covalently attached to DNA. Human small cell lung cancer NYH cells selected for resistance to ICRF-187 (NYH/187) showed a 25% increase in topoisomerase IIalpha level and no change in expression of the beta isoform. Sequencing of the entire topoisomerase IIalpha cDNA from NYH/187 cells demonstrated a homozygous G-->A point mutation at nucleotide 485, leading to a R162Q conversion in the Walker A consensus ATP binding site (residues 161-165 in the alpha isoform), this being the first drug-selected mutation described at this site. Western blotting after incubation with ICRF-187 showed no depletion of the alpha isoform in NYH/187 cells in contrast to wild-type (wt) cells, whereas equal depletion of the beta isoform was observed in the two sublines. Alkaline elution assay demonstrated a lack of inhibition of etoposide-induced DNA single-stranded breaks in NYH/187 cells, whereas this inhibition was readily apparent in NYH cells. Site-directed mutagenesis in human topoisomerase IIalpha introduced into a yeast Saccharomyces cerevisiae strain with a temperature-conditional yeast TOP2 mutant demonstrated that R162Q conferred resistance to the bisdioxopiperazines ICRF-187 and -193 but not to etoposide or m-AMSA. Both etoposide and m-AMSA induced more DNA cleavage with purified R162Q enzyme than with the wt. The R162Q enzyme has a 20-25% decreased catalytic capacity compared to the wt and was almost inactive at <0.25 mM ATP compared to the wt. Kinetoplast DNA decatenation by the R162Q enzyme at 1 mM ATP was not resistant to ICRF-187 compared to wt, whereas it was clearly less sensitive than wt to ICRF-187 at low ATP concentrations. This suggests that it is a shift in the equilibrium to an open-clamp state in the enzyme's catalytic cycle caused by a decreased ATP binding by the mutated enzyme that is responsible for bisdioxopiperazine resistance.

Neuroprotection by a novel compound, NS521.

NS521 (1-(1-butyl)-4-(2-oxo-1-benzimidazolinyl)piperidine) belongs to a group of novel benzimidazolones, which exhibit neurotrophic-like activities. In vitro, NS521 rescued neuronal PC12 cells from death induced by serum and nerve growth factor deprivation. The survival effect of NS521 appeared to reflect a delay of the apoptotic process, because the extent of DNA fragmentation was attenuated transiently by NS521. NS521 did not preserve the neurites of the rescued cells, which, otherwise, appeared to be healthy and were able to regenerate when serum and nerve growth factor were added back to the culture. In vivo, NS521 provided significant protection against the delayed loss of hippocampal CA1 neurons in a gerbil model of transient global ischemia. A neuroprotective effect of NS521 in the peripheral nervous system also was observed in rats after transection of the sciatic nerve, where daily treatment with NS521 was found to inhibit retrograde degeneration of the transected nerve. The neuroprotective effect of NS521 is unlikely to be mediated through neurotrophin receptors, such as TrkA, because NS521 did not induce phosphorylation of the 44- and 42-kDa isoforms of mitogen-activated protein kinases (ERK1/2) in PC12 cells.

SPD 502: a water-soluble and in vivo long-lasting AMPA antagonist with neuroprotective activity.

Accumulating preclinical data suggest that compounds that block the excitatory effect of glutamate on excitatory amino acid receptors may have neuroprotective effects and utility for the treatment of neurodegeneration after brain ischemia. In the present study, the in vitro and in vivo pharmacological properties of the novel glutamate antagonist SPD 502 [8-methyl-5(4-(N,N-dimethylsulfamoyl)phenyl)-6,7, 8,9,-tetrahydro-1H-pyrrolo[3,2-h]-isoquinoline-2, 3-dione-3-O-(4-hydroxybutyric acid-2-yl)oxime] are described. In binding studies, SPD 502 was shown to display selectivity for the [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-binding site (IC50 = 0.043 microM) compared with the [3H]kainate- (IC50 = 81 microM), [3H]cis-4-phosphonomethyl-2-piperidine carboxylic acid-(CGS 19755), and [3H]glycine-binding sites (IC50 > 30 microM) in rat cortical membranes. In an in vitro functional assay, SPD 502 blocked the AMPA-induced release of [3H]gamma-aminobutyric acid from cultured mouse cortical neurons in a competitive manner with an IC50 value of 0.23 microM. Furthermore, SPD 502 potently and selectively inhibited AMPA-induced currents in cortical neurons with an IC50 value of 0.15 microM. In in vivo electrophysiology, SPD 502 blocked AMPA-evoked spike activity in rat hippocampus after i.v. administration with an ED50 value of 6.1 mg/kg and with a duration of action of more than 1 h. Furthermore, SPD 502 increased the seizure threshold for electroshock-induced tonic seizures in mice at i.v doses of 40 mg/kg and higher. In the two-vessel occlusion model of transient forebrain ischemia in gerbils, SPD 502 (10 mg/kg bolus injection followed by a 10 mg/kg/h infusion for 2 h) resulted in a highly significant protection against the ischemia-induced damage in the hippocampal CA1 pyramidal neurons.

Ligands for the benzodiazepine binding site--a survey.

Gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian Central Nervous System (CNS). GABA participates in the regulation of neuronal excitability through interaction with specific membrane proteins (the GABAA receptors). The binding of GABA to these postsynaptic receptors, results in an opening of a chloride channel integrated in the receptor which allows the entry of Cl- and consequently leads to hyperpolarization of the recipient cell. The action of GABA is allosterically modulated by a wide variety of chemical entities which interact with distinct binding sites at the GABAA receptor complex. One of the most thoroughly investigated modulatory site is the benzodiazepine binding site. The benzodiazepines constitute a well-known class of therapeutics displaying hypnotic, anxiolytic and anticonvulsant effects. Their usefulness, however, is limited by a broad range of side effects comprising sedation, ataxia, amnesia, alcohol and barbiturate potentiation, tolerance development and abuse potential. Consequently, there has been an intensive search for modulatory agents with an improved profile, and a diversity of chemical entities distinct from the benzodiazepines, but with GABA modulatory effects have been identified. The existence of endogenous ligands for the GABAA receptor complex beside GABA has often been described, but their role in the regulation of GABA action is still a matter of controversy. The progress of molecular biology during the last decade has contributed enormously to the understanding of benzodiazepine receptor pharmacology. A total of 14 GABAA receptor subunits have been cloned from mammalian brain and have been expressed/co-expressed in stable cell lines. These transfected cells constitute an important tool in the characterization of subtype selective ligands. In spite of the rapidly expanding knowledge of the molecular and pharmacological mechanisms involved in GABA/benzodiazepine related CNS disorders, the identification of clinically selective acting drugs is still to come.

MPTP-induced Parkinsonism in minipigs: A behavioral, biochemical, and histological study.

Fourteen male Göttingen minipigs were used in this study. Nine were administered N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dosage of 1 mg/kg/day, SC, for 6 days, the last five pigs received saline injections for 6 days. All MPTP-treated animals developed Parkinson symptoms, i.e., muscle rigidity, hypokinesia, and impaired coordination within 5 days. The brain levels of dopamine (DA), and its major metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were determined in caudatum and putamen 2, 14, and 93 days (n = 3/time point) after the last drug administration. In eight of the MPTP-treated animals, striatal DA, DOPAC, and HVA concentrations were reduced from 50 to 95% compared to control animals at all time intervals. Animals with the lowest striatal DA concentrations showed the most severe signs of Parkinsonism. The number of cells in substantia nigra (SN) showed a decline only 3 months after MPTP treatment. The minipigs represent a nonprimate model of MPTP-induced parkinsonism syndromes lasting at least months.

In vivo and in vitro evaluation of AMPA receptor antagonists in rat hippocampal neurones and cultured mouse cortical neurones.

The effects of four glutamate receptor antagonists on alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)- and N-methyl-D-aspartate (NMDA)-responses were evaluated using both in vitro and in vivo electrophysiological techniques: whole cell patch-clamp recordings from cultured mouse cortical neurones and microiontophoresis in the rat hippocampus. The compounds tested were NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline), GYKI 52466 (1-(4-amino-phenyl)-4-methyl-7,8-methyl-endioxyl-5H-2,3-benzodiaze pine), PNQX (pyrido[3, 4-f]quinoxaline-2,3-dione, 1,4,7,8,9,10-hexahydro-9-methyl-6-nitro-, methanesulfonate), NS377 (7-ethyl-5-phenyl-1,6,7,8-tetrahydro-1,7-diaza-as-indacene-2 ,3-dione), and MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenz(a,d)cycloheptene-5,10-imine hydrogen maleate). In vitro, the IC50 values (in microM) for inhibition of AMPA-evoked inward currents were approximately 0.4 for NBQX, approximately 7.5 for GYKI 52466, approximately 1 for PNQX and approximately 15 for NS377. PNQX and NS377 also inhibited NMDA-induced currents with IC50 values at approximately 5 and approximately 18 microM, respectively, while NBQX at 60 microM and GYKI 52466 at 100 microM had only weak effects. The ED50 values in micromol/kg i.v. for inhibition of AMPA-evoked hippocampal neuronal spike activity in vivo were approximately 32 for NBQX, approximately 19 for GYKI 52466, approximately 17 for PNQX and approximately 11 for NS377 with efficacy values (maximal inhibition) between 71% and 81%. The ED50 values (in [Lmol/kg i.v.) and efficacy values for inhibition of NMDA-evoked hippocampal neuronal spike activity were approximately 28 with an efficacy of 61% for NBQX, approximately 16 with 35% for PNQX and approximately 6 with 61% for NS377. GYKI 52466 did not significantly affect NMDA responses, whereas MK-801 showed NMDA specificity in vivo.