SummaryThe present trial was designed to comparatively investigate the pharmacokinetic profile and evaluate the apparent bioavailability pattern of three already marketed low molecular mass heparins (LMMHs): dalteparin (Fragmin®), nadroparin (Fraxiparin®), and enoxaparin (Love- nox®) given by subcutaneous route. The study was carried out in 20 healthy young volunteers given, according to a cross over design, a single subcutaneous injection of the doses recommended for the prophylaxis of deep vein thrombosis (commercial preparations, prefilled syringes): dalteparin 2,500 IU (= 2,500 IU anti-Xa), nadroparin 7,500 ICU (= 3,075 IU anti-Xa), enoxaparin 20 mg (= 2,000 IU anti-Xa) and enoxaparin 40 mg (= 4,000 IU anti-Xa). Of the markers used, activated partial thromboplastin time (APTT), thrombin clotting time (TCT), Heptest®, anti-thrombin (aIIa) activity and anti-Xa (aXa) activity, the most pertinent parameter (from a biodynamic viewpoint) is plasma aXa activity. We demonstrated that dalteparin, nadroparin and enoxaparin exhibit statistically significantly different pharmacokinetic and overall disposition patterns. Normalized to the same injected dose (1,000 IU aXa), the relative actual amount of plasma anti-Xa activity generated by enoxaparin is 1.48 times greater (p < 0.001) than that of nadroparin and 2.28 times greater (p < 0.001) than that of dalteparin while the plasma amount induced by nadroparin is 1.54 times greater (p < 0.001) than that of dalteparin. The apparent total body clearance of enoxaparin doses (CL/F = 16.7 ± 5.5 and 13.8 ± 3.2 ml/min) is significantly smaller than those of nadroparin (CL/F = 21.4 ± 7.0 ml/min ; p < 0.01) and dalteparin (CL/F = 33.3 ±11.8 ml/min ; p < 0.001) while dalteparin apparent clearance is about 1.5-fold greater (p < 0.001) than that of nadroparin. These LMMHs also differ by their renal excretion pattern : more fragments exhibiting an anti-Xa activity are recovered in urine following enoxaparin doses (6.4 and 8.7 % of the dose, respectively) than following nadroparin (3.9 %) and dalteparin (3.4 %) injection. These differences in the disposition profiles explain why the apparent elimination half life t1/2 values of the LMMHs compared here are different: dalteparin: 2.8 h; nadroparin: 3.7 h; and enoxaparin: 4.1 h. Whether or not these differences may contribute to explain the different safety/efficacy balance of each of these antithrombotic medications remains to be discussed and needs further studies.

The identification of adverse health effects has a central role in the development and risk/safety assessment of chemical entities and pharmaceuticals. There is currently a need for better alignment regarding how nonclinical adversity is determined and characterized. The European Society of Toxicologic Pathology (ESTP) therefore coordinated a workshop to review available definitions of adversity, weigh determining and qualifying factors of adversity based on case examples, and recommend a practical approach to define and characterize adversity in toxicology reports, to serve as a valuable prerequisite for future organ-or lesion-specific workshops planned by the ESTP.

SummaryWe determined, in volunteers, the plasma levels of heparin above and below the critical chainlength necessary for thrombin inhibition (ACLM and BCLM), from 1 to 24 h after subcutaneous injection of 5000IU unfractionated heparin (UFH), 40 mg enoxaparin and 1 mg/kg body weight of enoxaparin (LMWH) (n = 12 for each dose). The levels were calculated from the antithrombin- and anti-Xa activities using the specific activities of the materials injected. We also determined the course of thrombin- and of factor Xa generation after triggering the extrinsic system in the same samples. From the thrombin generation curves, we calculated the course of prothrombinase activity.When the ACLM and BCLM plasma-levels are plotted against the inhibition of thrombin- and factor Xa generation, it appears that:a) There is a unique dose response relationship between ACLM level and the inhibition of thrombin generation, independent of whether the ACLM is derived from UFH or LMWH. This relationship is not significantly altered by the BCLM appearing after LMWH injection.b) There is a similar unique relationship between ACLM level and the inhibition of factor Xa generation, again independent of BCLM.c) Inhibition of prothrombin activation hardly contributes to the overall effect on thrombin formation and is again independent of the source of ACLM.d) ACLM levels were significantly higher after injection of LMWH than after UFH injection, even though the amounts of ACLM injected with the highest dose of LMWH were smaller than those administered in the UFH injection.We conclude that the only functional difference between LMWH and UFH is the much higher bioavailability of the former. We surmise that, from the UFH injected, only the lower molecular weight species reach the circulation, i. e. a fraction similar to the ACLM injected with enoxaparin.

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As dronedarone a new noniodinated antiarrhythmic agent structurally related to amiodarone could inhibit CYP2D6 and is planned to be associated with beta-blockers, interactions with CYP2D6 metabolized beta-blockers such as metoprolol, have to be studied. Forty-nine healthy male subjects genotyped for CYP2D6 were included in a randomized, double-blind, placebo-controlled study. Metoprolol was administrated during 13 days (200 mg/day). After the initial 5 days, subjects received placebo (n = 12), 800 mg (n = 6), 1200 mg (n = 9), or 1600 mg (n = 17) of dronedarone daily during eight additional days. Pharmacokinetic parameters of metoprolol were investigated at day 5 and at day 13 in 44 subjects, 39 extensive metabolizers and five poor metabolizers for CYP2D6. Cardiac contractility function was evaluated by the rate-corrected electromechanical systole duration (QS2i) and the mean velocity of endocardial circumferential fiber shortening (Vcfmean). Cmax and AUC0--24 h of metoprolol increased from days 5 to 13 in proportion to dronedarone dose only in CYP2D6 extensive metabolizers genotyped subjects (P < 0.001). In all subjects, from days 5 to 13, Vcfmean decreased and QS2i significantly increased in dronedarone groups. The Vcfmean changes were however significant only with the 1600 mg dronedarone dose compared with placebo while QS2i changes induced by addition of dronedarone were significant compared with placebo at all dose levels. Between days 5 and 13, QS2i and Vcfmean changes were significantly correlated with both dronedarone concentrations at day 13 and with metoprolol concentration changes between days 5 and 13. Plasma metoprolol concentrations were highest in poor metabolizer subjects and dronedarone did not further increase their level but increased QS2i in the two subjects receiving the 1600 mg dose. Addition of dronedarone (800-1600 mg daily) to metoprolol (200 mg daily) increases bioavailability of metoprolol in CYP2D6 extensive metabolizers and induces an additive dronedarone dose-dependent negative inotropic effect. Nevertheless at 800 mg daily (anticipated therapeutic dose) these effects were modest.

Some cases of spontaneous bleeding have been reported in patients treated with Ginkgo biloba. A prospective, double-blind, randomized, placebo-controlled study was carried out in 32 young male healthy volunteers to evaluate the effect of three doses of Ginkgo biloba extract (120, 240 and 480 mg/day for 14 days) on hemostasis, coagulation and fibrinolysis. This study did not reveal any alteration of platelet function or coagulation. This suggests that the reported clinical bleeding events in patients receiving Ginkgo biloba extract are not related to pharmacological properties of EGb761.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • After the TGN1412 incident in London, the European authorities reinforced the safety requirements for first‐entry‐into‐man (FIM) studies. Their recommendations on risk management included a risk minimization strategy based on clearly defined stopping rules. However to date, there are no approved grading scales for clinical adverse events or safety findings to support dose escalation and to define stopping rules in order to mitigate the risks for healthy subjects participating in FIM trials. WHAT THIS STUDY ADDS • This paper proposes standardized methods for the grading of safety data (adverse events, laboratory tests, electrocardiogram and vital sign findings) based on relevant criteria. The proposed grading scale provides support both for dose escalation and the design of stopping rules. The derived safety thresholds are applicable at either an individual subject level or at a cohort level, and are specifically adapted to young male healthy subjects, who represent the majority of the subjects participating in FIM trials. AIM To propose a relevant grading scale for clinical adverse events or laboratory results, electrocardiogram (ECG) and vital sign findings supporting both dose escalation and stopping decisions in first‐entry‐into‐man (FIM) studies conducted in young healthy subjects. METHODS A three‐level scale was used for the proposed grading system. The grading is directly derived from the observed severity of discontinuous variables, as are most of clinical adverse events. A ‘combined method’ based on normal ranges and spontaneous variation is suggested for grading the findings which are continuous variables mainly numerical in nature. One grade, at the subject level, and one algorithm, at the cohort level, support the proposed decision rules. This work was managed by a Club Phase I working group. RESULTS Examples of grade 1, 2 and 3 limits are given for the most frequent clinical adverse events and laboratory tests, ECG and vital sign findings. When available, the proposed NIH and FDA limits are also provided. The safety recommendation is to use the grade 2 at least as an alert for caution and the grade 3 as a maximum for stopping, applying the algorithm at the cohort level. CONCLUSIONS This paper proposes a safety grading system based on relevant criteria which might be used by investigators and sponsors to support and rationalize dose escalation decisions in healthy young subject FIM studies. These proposals are designed not to be a guideline but some ‘points to consider’ helping the dose escalation process. This paper supports the recent reinforcement of the safety requirements for FIM studies by European authorities.

SummaryWe administered a dose of unfractionated heparin (UFH) and two doses of a low molecular weight heparin (LMWH) to healthy volunteers by SC injection. The doses given were: a) UFH, 5000IU, which represents 8.7 mg of >5,400 MW active heparin (ACLM) and no <5,400 active heparin (BCLM), b) enoxaparin 40 mg (3.4 mg ACLM, 2.2 mg BCLM) and c) enoxaparin 1 mg/kg body weight (on the mean 75 mg, containing 6.4 mg ACLM and 4.1 mg BCLM). We determined the effect on thrombin generation in platelet rich plasma (PRP) between 1 and 8 h after injection. UFH administration caused only a 5-8% inhibition of the thrombin potential (i. e. the area under the thrombin generation curve). Significantly higher inhibition of the thrombin potential was seen after administration of both doses of enoxaparin. To wit 9-26% at the low dose and 29-46% at the high dose. UFH injection caused a prolongation of the lag-time before the thrombin burst. Only with the high dose of enoxaparin the lag-times were significantly more prolonged with enoxaparin than with UFH.Excess amounts of platelet factor 4 (PF4) were able to neutralize completely the anti-thrombin activity in normal plasma spiked with enoxaparin as well as in plasma samples obtained after SC enoxaparin injection. With a large excess of PF4 the anti-factor Xa activity could be inhibited to a maximum of 50%. This indicates that ACLM (above critical length material, MW >5400) is neutralized completely by PF4 whereas BCLM (below critical length material, MW <5400) is not. The anti-thrombin heparin-activity, hence the ACLM fraction of heparin, was shown to have disappeared from the serum of PRP samples. The BCLM fraction was found after coagulation of PRP in concentrations that were indistinguishable from those in the PPP.We conclude that in PRP the activity of the BCLM fraction of injected LMWH remains after platelet activation. The possible role of this activity in thrombin inhibition and in the antithrombotic action of low molecular weight heparins is discussed.