scholarly journals An open label, adaptive, phase 1 trial of high-dose oral nitazoxanide in healthy volunteers: an antiviral candidate for SARS-CoV-2

2021 ◽  
Author(s):  
Lauren E Walker ◽  
Richard FitzGerald ◽  
Geoffrey Saunders ◽  
Rebecca Lyon ◽  
Michael Fisher ◽  
...  
Keyword(s):  
Phase 1 ◽  
Optimum Dose ◽  
Drug Discontinuation ◽  
High Dose ◽  
Open Label ◽  
Pbpk Modelling ◽  
Health Crisis ◽  
Phase 1 Trial

AbstractRepurposing approved drugs may rapidly establish effective interventions during a public health crisis. This has yielded immunomodulatory treatments for severe COVID-19, but repurposed antivirals have not been successful to date because of redundancy of the target in vivo or suboptimal exposures at studied doses. Nitazoxanide is an FDA approved antiparasitic medicine, that physiologically-based pharmacokinetic (PBPK) modelling has indicated may provide antiviral concentrations across the dosing interval, when repurposed at higher than approved doses. Within the AGILE trial platform (NCT04746183) an open label, adaptive, phase 1 trial in healthy adult participants was undertaken with high dose nitazoxanide. Participants received 1500mg nitazoxanide orally twice-daily with food for 7 days. Primary outcomes were safety, tolerability, optimum dose and schedule. Intensive pharmacokinetic sampling was undertaken day 1 and 5 with Cmin sampling on day 3 and 7. Fourteen healthy participants were enrolled between 18th February and 11th May 2021. All 14 doses were completed by 10/14 participants. Nitazoxanide was safe and well tolerated with no significant adverse events. Moderate gastrointestinal disturbance (loose stools) occurred in 8 participants (57.1%), with urine and sclera discolouration in 12 (85.7%) and 9 (64.3%) participants, respectively, without clinically significant bilirubin elevation. This was self-limiting and resolved upon drug discontinuation. PBPK predictions were confirmed on day 1 but with underprediction at day 5. Median Cmin was above the in vitro target concentration on first dose and maintained throughout. Nitazoxanide administered at 1500mg BID with food was safe and well tolerated and a phase 1b/2a study is now being initiated in COVID-19 patients.

scholarly journals An open label, adaptive, phase 1 trial of high‐dose oral nitazoxanide in healthy volunteers: an antiviral candidate for SARS‐CoV‐2

2021 ◽  
Author(s):  
Lauren E Walker ◽  
Richard FitzGerald ◽  
Geoffrey Saunders ◽  
Rebecca Lyon ◽  
Michael Fisher ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Phase 1 ◽  
High Dose ◽  
Open Label ◽  
Phase 1 Trial ◽  
Dose Oral

Randomized, multicenter, two-dose level, open-label, phase IIa study with the intraperitoneally infused trifunctional bispecific antibody catumaxomab (anti-EpCAM × anti-CD3) to select the better dose level in platinum refractory epithelial ovarian cancer patients

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 5556-5556 ◽  
Author(s):  
A. Belau ◽  
J. Pfisterer ◽  
P. Wimberger ◽  
C. Kurzeder ◽  
A. Du Bois ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Epithelial Ovarian Cancer ◽  
Dose Level ◽  
Dose Effect ◽  
High Dose ◽  
Specific Cell ◽  
Open Label ◽  
Platinum Refractory

5556 Background: The trifunctional antibody catumaxomab specifically binds EpCAM+ tumor cells, CD3+ T lymphocytes and accessory cells via the Fcγ RI/III thereby inducing a tumor specific cell mediated cytotoxicity in vitro and in vivo. This study was conducted to evaluate efficacy and safety of two different regimens of catumaxomab. Methods: Women with platinum-refractory (progressing during or ≤ 6 mos. after the last platinum containing regimen) epithelial ovarian cancer and measurable recurrent disease were randomized to receive either 10 -10 -10 - 10 μg or 10–20–50–100 μg of catumaxomab over 6h i.p on days 0, 3, 7 and 10. Results: 45 pts. were entered (22 high dose (HD)-arm, 23 low dose (LD)-arm). Both groups were well balanced concerning ECOG-perfomance score, with a median age of 65.6y in the HD- and 57.6y in the LD-arm and with a median diameter of measurable lesions of 90mm in the HD- and 104mm in the LD-arm. Based on the AEs, changes in laboratory parameters and other safety variables observed in the safety population in the course of this study, the accumulated safety experience is consistent with the key features of the mode of action of catumaxomab. Their intensity on median level was mostly mild to moderate. A clinical benefit was detectable in 27.3% of pts. for the HD- (1PR/5SD) and 8.7% of pts. for the LD-arm (2SD). After a median follow-up of 4.96 months, the median overall survival time was 182 d for the HD- and 114 d for the LD-arm. Conclusion: The results demonstrate that catumaxomab is safe with acceptable toxicity when administered as a sequence of 4 IP infusions at 10, 20, 50 and 100 μg. A modest dose effect is observed for the higher doses of catumaxomab. No significant financial relationships to disclose.

Results of a phase I study to evaluate the feasibility, safety, and biological effects of intravenous administration of wild-type reovirus with docetaxel to patients with advanced malignancies

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e13524-e13524
Author(s):  
S. M. Rudman ◽  
C. Comins ◽  
D. Mukherji ◽  
M. Coffey ◽  
K. Mettinger ◽  
...  
Keyword(s):  
Phase I ◽  
Biological Effects ◽  
Phase 1 ◽  
Maximum Tolerated Dose ◽  
Wild Type ◽  
Systemic Delivery ◽  
Open Label ◽  
Phase Ii Studies

e13524 Background: Reovirus has minimal pathogenicity in humans but selectively replicates in cells with activated Ras. Wild- type reovirus serotype 3 Dearing strain (Reolysin) has selective antitumor activity in vitro, in murine models, and after systemic delivery in humans in phase 1 trials. Synergistic tumour kill has been observed combining reovirus with taxanes in a range of cancer cell lines and in vivo. Methods: Patients were treated in an open-label, dose-escalating, phase I trial and received 3- weekly 75mg/m2 docetaxel i.v. and reovirus i.v. (day 1–5 of first week inclusive). Reovirus was administered at a starting dose of 3x109 tissue culture infectious dose (TCID50) and then increased to 1 x 1010 and 3 x 1010 TCID50. Primary endpoints were to determine the maximum tolerated dose (MTD), dose limiting toxicity (DLT) and to recommend a dose and schedule for future investigation. Secondary endpoints were to evaluate pharmacokinetics, neutralizing antibody development, cell- mediated immune response and anti-tumour activity. Results: 17 patients were treated (15 males, median age 60 years). No MTD has been reached. DLT's observed were G4 neutropenia (and a recurrent perianal abcess) and G3 rise in AST. Other toxicities observed were fatigue, hypotension and neutropenic sepsis. At present, 5 patients remain on treatment. We have observed 2 partial responses (breast and gastric carcinoma) and 10 patients had stable disease as best response. Conclusions: Reovirus is well tolerated when administered in combination with intravenous docetaxel, with predictable toxicity observed. The recommended dose has been defined at 3x1010 TCID50 and phase II studies are planned. Objective radiological evidence of anticancer activity for this combination has been observed. [Table: see text]

Safety, efficacy, and pharmacodynamics of the investigational agent orteronel (TAK-700) in metastatic castration-resistant prostate cancer (mCRPC): Updated data from a phase I/II study.

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 98-98 ◽  
Author(s):  
David B. Agus ◽  
Walter Michael Stadler ◽  
Daniel H. Shevrin ◽  
Lowell Hart ◽  
Gary R. MacVicar ◽  
...  
Keyword(s):  
Phase 1 ◽  
Specific Antigen ◽  
Response Rates ◽  
Similar Efficacy ◽  
Castration Resistant Prostate Cancer ◽  
Open Label ◽  
Investigational Agent ◽  
Psa Response

98 Background: The investigational agent orteronel (TAK-700) is a selective 17,20 lyase inhibitor that down regulates androgenic steroid production in vitro and in vivo. Since phase 1 data in patients (pts) with mCRPC were promising, this open-label, multicenter study was expanded to gather additional data on safety and antitumor activity. Methods: The phase 2 portion of this study included four additional dose cohorts. Pts had no prior chemotherapy, and had baseline testosterone <50 ng/dL and prostate-specific antigen (PSA) ≥5 ng/mL. Results: 97 pts received orteronel 300 mg BID (n=23), 400 mg BID + prednisone 5 mg BID (n=24), 600 mg BID + prednisone (n=26), or 600 mg QD (n=24). At data cut-off (23 May 2011), 62% of pts had withdrawn (including 19% due to AEs and 19% for disease progression [PD]). Most common AEs were fatigue (76%), nausea (47%), and constipation (38%); most common grade ≥3 AEs were fatigue (12%) and hypokalaemia (8%). PSA response rates (≥50% decrease) at 12 wks were 63%, 50%, 41%, and 60% in the 300 mg BID, 400 and 600 mg BID + prednisone, and 600 mg QD groups. Of 51 RECIST-evaluable pts, 10 had partial responses (of which 5 confirmed), 22 stable disease, and 15 PD. At 12 wks, median testosterone decreased from baseline in all groups: (ng/dL, 12 wks/baseline) 0.98/8.50 (300 mg BID), 0.30/9.90 (400 mg BID +prednisone), 0.07/7.33 (600 mg BID + prednisone), 0.49/6.31 (600 mg QD). Similarly, at 12 wks, median dehydroepiandrosterone sulfate (DHEA-S) decreased from baseline in all groups: (µg/dL, 12 wks/baseline) 8.65/53.0 (300 mg BID), 0.10/36.3 (400 mg BID + prednisone), 0.10/51.7 (600 mg BID + prednisone), 5.30/31.5 (600 mg QD). Overall, mean circulating tumor cell numbers decreased from 16.6 (per 7.5mL blood) at baseline to 3.9 at 12 wks. Conclusions: Orteronel ≥300 mg BID appears active and well tolerated in pts with mCRPC, with similar efficacy ± prednisone. PSA response rates suggest that testosterone, rather than DHEA, may be a more reliable marker of lyase inhibition efficacy. Preclinical data and changes in pharmacodynamic parameters in this study suggest partially selective 17,20 lyase inhibition. Final data will be reported.

Ensituximab (E) in patients (pts) with refractory metastatic colorectal cancer (mCRC): Results of a phase I/II clinical trial.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. 3081-3081 ◽  
Author(s):  
Richard D. Kim ◽  
Philip M. Arlen ◽  
Kwong Y. Tsang ◽  
Sharon Mavroukakis ◽  
Anjum Zaki ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Clinical Trial ◽  
Phase 1 ◽  
Pancreatic Cancer Cell Line ◽  
Cancer Cell Line ◽  
Serum Cytokine ◽  
Open Label ◽  
Related Factors

3081 Background: E is an investigational, novel, chimeric monoclonal IgG1 antibody derived from an immunogenic neoantigen with sequence homology to MUC5AC that is preferentially expressed with exquisite specificity to pancreatic cancer and CRC. Its mechanism of action is via antibody-dependent cellular cytotoxicity (ADCC). The efficacy and safety of E was evaluated in a single-arm, open-label, phase 1/2 clinical trial of adult pts with refractory mCRC. Methods: Pts were selected based on > 20% expression of tumor antigen, as measured by immunohistochemistry. Based on phase 1 results, E was administered 3 mg/kg IV every 2 weeks until unacceptable toxicity or disease progression. Primary endpoint was overall survival (OS). Serum cytokine levels were analyzed at baseline, day 4, and day 15. E-mediated ADCC of CD16 genotype V/V, V/F, and F/F pt PBMCs was measured with an IN-111 release assay using the E target-expressing ASPC-1 pancreatic cancer cell line. Results: Fifty-seven and 63 pts were evaluable for OS and safety, respectively. Median OS was significantly longer than historical control: 6.8 vs 5.0 months (mo); p = 0.007; 95% CI: 5.39,8.02. Three pts were alive at end of study (21, 21, and 24 mo); 21 pts survived ≥ 12 mo. Pts had a median of 4 prior therapies (range 2-9); 25% had received regorafenib. Forty-seven pts were evaluable by RECIST, and 20 (43%) had stable disease of target lesions at end of first course (day 57). E was well tolerated, with < 2% grade 3 and no grade 4 toxicities. There were no trends in serum cytokine and chemokine levels. Analysis of 56 samples (8 V/V, 26 V/F, 17 F/F, and 5 undetermined) showed that V/V PBMCs had significantly higher E-mediated ADCC than PBMCs harboring other genotypes. No correlation between CD16 polymorphism and pt outcome was observed. Conclusions: E demonstrated excellent tolerability and encouraging OS in this heavily pretreated population. Correlative in vitro data suggest that E can mediate higher levels of ADCC activity in individuals with a V/V versus other genotypes. The lack of correlation between CD16 polymorphism and pt outcomes in this study suggests that other immune-related factors (under investigation) may impact the efficacy of E in vivo. Clinical trial information: NCT01040000.

An open-label, multicenter, phase I/II study of AT-101 in combination with docetaxel (D) and prednisone (P) in men with castrate-resistant prostate cancer (CRPC)

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 5062-5062
Author(s):  
G. R. MacVicar ◽  
A. Greco ◽  
J. Reeves ◽  
J. Maleski ◽  
J. Holmlund ◽  
...  
Keyword(s):  
Adverse Events ◽  
Phase 1 ◽  
Single Agent ◽  
Safety Data ◽  
Preliminary Evidence ◽  
Open Label ◽  
Serious Adverse Events ◽  
Vein Thrombosis

5062 Background: Antiapoptotic Bcl-2 family proteins are overexpressed in CRPC and contribute to resistance to therapy. The oral pan-Bcl-2 inhibitor AT-101 (Bcl-2, Bcl-XL, Bcl-W, Mcl-1) is active as a single agent and in combination in in vitro and in vivo tumor models and as a single agent in CRPC. The Phase 1 portion of the study determined the recommended dose for phase II to be D (75mg/m2 q3weeks) in combination with P (5mg b.i.d. on days 1–21), and AT-101 at 40mg b.i.d. on days 1–3 of each 21-day cycle, and was previously reported. Methods: Men ≥18 years of age with chemotherapy-naïve CRPC (N = 36). Safety (NCI CTCAE v3.0) and efficacy (Bubley Criteria for PSA) were assessed at 3-wk intervals. Radiological assessments were performed at 6-wk intervals for pts with soft tissue disease and bone scans were performed after cycle 6 and at the completion of therapy. Results: 36 patients (pts) have been enrolled in the study. Twenty-four (67%) pts achieved a partial response (PR) (>50% PSA decline), and 26 (72%) pts treated had at least a 30% decrease in PSA level. Nine of 19 pts (47%) with measurable disease had a PR. One PR was unconfirmed per RECIST. Thirteen pts (36%) completed >10 cycles of therapy (range 2–24) thus far. Four pts remains active. Safety data is available for 31 pts. The most common (>20%) Adverse Events (AEs) include: fatigue (68%), nausea (52%), diarrhea (45%), alopecia (32%), constipation and dysgeusia (26%), and neutropenia and vomiting (26%). Neutropenia was the only gr. 4 event occurring in more than one pt (3pts). Serious Adverse Events (SAEs) considered related were reported in 5 pts (16%). The only SAEs reported in 2 or more pts were urinary tract infection (3 pts) and deep vein thrombosis (2 pts) and none were considered related. No ileus has been reported. Conclusions: AT-101 when given in combination with D/P is well tolerated and shows preliminary evidence of efficacy in pts with CRPC. A randomized trial is ongoing. [Table: see text]

BBI608-224: A phase Ib/II study of cancer stemness inhibitor napabucasin (BBI-608) administered with panitumumab in KRAS wild-type patients with metastatic colorectal cancer.

2017 ◽  
Vol 35 (4_suppl) ◽  
pp. 677-677 ◽  
Author(s):  
Tim Larson ◽  
Waldo Feliu Ortuzar ◽  
Tanios S. Bekaii-Saab ◽  
Carlos Becerra ◽  
Kristen Keon Ciombor ◽  
...  
Keyword(s):  
Phase Ii ◽  
Phase 1 ◽  
Open Label ◽  
Cancer Stemness ◽  
Anti Cancer ◽  
Previously Treated ◽  
Multi Center Study ◽  
Anti Tumor Activity

677 Background: Napabucasin a first-in-class cancer stemness inhibitor in clinical development, suppresses cancer stemness by targeting Stat3-driven gene transcription. Preclinically, potent and broad-spectrum anti-cancer activity was observed in vitro and in vivo, alone and in combination with other agents. In a phase 1 study, napabucasin monotherapy was well tolerated with encouraging signs of anti-tumor activity at the RP2D of 500 mg BID. Methods: The current open-label, multi-center study includes phase II expansion in pts with refractory, K- Raswt mCRC to confirm safety and anti-tumor activity of napabucasin administered orally at 480mg BID in combination with panitumumab (6mg/kg bi-weekly). Results: 72 pts were enrolled, 48 pts were evaluable by RECIST of which 7 (15%) and 41 (85%) had 2 or >3 prior treatment lines, respectively. Of the 48 evaluable pts, 64.6% (31/48) were previously treated with an anti-EGFR agent. No new adverse events (AEs) were observed and most common AEs included grade 1/2 diarrhea, nausea, abdominal cramps, and vomiting. Among 48 pts enrolled who received RECIST evaluation, Disease Control Rate (DCR) was observed in 25 pts (52.1%) of which 3 pts achieved PR (6%) and 22 pts achieved SD (45%). Among 31 pts previously treated with anti-EGFR therapy, DCR was observed in 15 pts (48%) compared with DCR of 59% observed in 10 out of 17 anti-EGFR naïve pts receiving a scan. Conclusions: This phase II study confirmed that napabucasin can be safely combined with panitumumab at full dose and shows encouraging anti-tumor activity in pts with K- Ras wt mCRC, regardless of prior anti-EGFR exposure, suggesting that napabucasin may sensitize pts to repeat anti-EGFR therapy. Clinical trial information: NCT01776307. [Table: see text]

Phase 1 results of PTC596, a novel small molecule targeting cancer stem cells (CSCs) by reducing levels of BMI1 protein.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. 2574-2574 ◽  
Author(s):  
Jeffrey R. Infante ◽  
Philippe L. Bedard ◽  
Geoffrey Shapiro ◽  
Todd Michael Bauer ◽  
Amy Prawira ◽  
...  
Keyword(s):  
Phase 1 ◽  
Plasma Concentrations ◽  
Maximum Tolerated Dose ◽  
Open Label ◽  
In Vivo Models ◽  
Best Response ◽  
Gastrointestinal Side Effects ◽  
Anti Tumor Activity

2574 Background: PTC596 is an oral investigational new drug that reduces levels of BMI1, a protein required for CSC survival. PTC596 reduced the number of CSCs in preclinical models and slowed growth rates of tumor xenografts in rodent models. The primary objectives of this first-in-human trial of PTC596 were to determine safety, dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), and pharmacokinetics (PK). Secondary objectives included exploratory assessments of biological efficacy, pharmacodynamic changes and anti-tumor activity. Methods: A Phase I multi-center, open-label study was conducted in patients with advanced solid tumors using a modified 3+3 design, followed by a dose-confirmatory 10-patient expansion. PTC596 was administered using bodyweight-adjusted twice-per-week (biw) oral dosing in 4 week cycles. Dose escalation and MTD were based on observed cycle 1 DLTs. Anti-tumor activity was assessed by RECIST 1.1. Results: A total of 31 patients with a broad range of tumor types were enrolled at dose levels of 0.65 (N = 3), 1.3 (N = 3), 2.6 (N = 3), 5.2 (N = 11), 7 (N = 8) and 10 mg/kg (N = 3). Nausea, vomiting, and diarrhea were the most common all grade adverse events, though usually mild and manageable. At 10 mg/kg one patient experienced DLTs of neutropenia, mucositis, and thrombocytopenia. The other two patients at this dose level also experienced poor tolerability with Grade 2 nausea, vomiting, and diarrhea that may be partially due to the overall pill burden and excipients. The recommended dose for the expansion and further study was 7 mg/kg. Over the dosing range, plasma concentrations of PTC596 increased in an approximately dose-proportional manner and at doses of 2.6 mg/kg and above exceeded those associated with activity in vitro and in vivo models. Best response was stable disease in 5 patients including two with minor radiographic reductions in tumor volume. Conclusions: PTC596 is tolerable with manageable gastrointestinal side effects. At 7 mg/kg biw exposures exceeded those associated with preclinical activity and future clinical studies are planned for this first-in class molecule that targets CSCs. Clinical trial information: NCT02404480.

A phase II study of ADI-PEG 20 and FOLFOX6 in patients (pts) with advanced hepatocellular carcinoma (HCC).

2019 ◽  
Vol 37 (4_suppl) ◽  
pp. TPS477-TPS477 ◽  
Author(s):  
James J. Harding ◽  
Shukui Qin ◽  
Tsai-Sheng Yang ◽  
Chia-Jui Yen ◽  
Yee Chao ◽  
...  
Keyword(s):  
Phase 1 ◽  
Objective Response ◽  
Arginine Deiminase ◽  
Clinical Activity ◽  
Advanced Hepatocellular Carcinoma ◽  
Phase 2 ◽  
Open Label ◽  
Cross Sectional

TPS477 Background: Arginine depletion interferes with pyrimidine metabolism as well as DNA damage repair pathways, and preclinical data indicate that pairing pegylated arginine deiminase (ADI-PEG 20) with fluoropyrimidines or platinum enhances cytotoxicity in vitro and in vivo in HCC models. A prior phase 1 study of FOLFOX6 and ADI-PEG 20 established the safety and recommended phase 2 dose of the combination in pts with advanced gastrointestinal tumors (Harding et al. CCP 2018). For 23 treatment-refractory HCC pts who were treated at the recommended phase 2 dose on an expansion cohort of the phase 1, the objective response rate (ORR) was 21% (95% CI 7.5-43.7) and median progression-free survival (PFS) was 7.3 months. These data were favorable when compared to historic data for FOLFOX alone where the ORR was ~8% and PFS was 2.93 months and suggest greater clinical activity of the combination (Qin et al. JCO 2013). Prospective confirmation of these results is required. Methods: This is an international, multicenter, single-arm, open-label phase 2 trial of ADI-PEG 20 and FOLFOX6 for advanced HCC pts with Child-Pugh A liver function who progressed on ≥ 2 prior lines of prior systemic therapy (NCT02102022). The primary objective is to define the ORR by RECIST 1.1 as assessed by blinded independent central review. Secondary objectives include determination of safety, disease control rate (DCR), duration of response (DOR), PFS, overall survival (OS), serum arginine, citrulline and anti-ADI-PEG 20 levels over 24 weeks, and alpha-fetoprotein response. Eligible pts receive intravenous FOLFOX6 biweekly at standard doses and ADI-PEG 20 intramuscularly weekly at 36 mg/m.2 Cross-sectional imaging will be completed every 8 weeks until progression of disease. Based on a two-sided exact test of a one-sample proportion with an alpha of 0.05, under a presumed ORR of 22%, there is 80% power to yield 95% confidence interval of 15-26%, which will require 46 objective responses in 225 subjects. Futility will be assessed three times during the study based on having ORR data available for 56, 110, and 166 patients. This Phase 2 will be stopped for futility if the conditional power drops below 20% at any of these time points. Clinical trial information: NCT02102022.

Significance of Platelet β-Adrenoceptors for Platelet Responses In Vivo and In Vitro

1992 ◽  
Vol 68 (06) ◽  
pp. 687-693 ◽  
Author(s):  
P T Larsson ◽  
N H Wallén ◽  
A Martinsson ◽  
N Egberg ◽  
P Hjemdahl
Keyword(s):  
Ex Vivo ◽  
High Dose ◽  
Platelet Aggregability ◽  
Adrenoceptor Agonist ◽  
Dose Infusion ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Factor Antigen

SummaryThe significance of platelet β-adrenoceptors for platelet responses to adrenergic stimuli in vivo and in vitro was studied in healthy volunteers. Low dose infusion of the β-adrenoceptor agonist isoprenaline decreased platelet aggregability in vivo as measured by ex vivo filtragometry. Infusion of adrenaline, a mixed α- and β-adrenoceptor agonist, increased platelet aggregability in vivo markedly, as measured by ex vivo filtragometry and plasma β-thromboglobulin levels. Adrenaline levels were 3–4 nM in venous plasma during infusion. Both adrenaline and high dose isoprenaline elevated plasma von Willebrand factor antigen levels β-Blockade by propranolol did not alter our measures of platelet aggregability at rest or during adrenaline infusions, but inhibited adrenaline-induced increases in vWf:ag. In a model using filtragometry to assess platelet aggregability in whole blood in vitro, propranolol enhanced the proaggregatory actions of 5 nM, but not of 10 nM adrenaline. The present data suggest that β-adrenoceptor stimulation can inhibit platelet function in vivo but that effects of adrenaline at high physiological concentrations are dominated by an α-adrenoceptor mediated proaggregatory action.

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