Steven Glazer

Clinical Experience with Recombinant Factor VIla in Patients with Thrombocytopenia

Platelets play a central role in primary hemostasis. The role of the coagulation mechanism during early stages of hemostasis is less clear, although increasing evidence is emerging indicating the ultimate importance of the factor VII (FVII)-tissue factor-dependent coagulation system in providing the first thrombin molecules necessary for the platelet activation to occur. Supporting this, early fibrin formation has been reported to occur within the bleeding time wound and infusion of recombinant FVIIa (rFIIa) has been shown to shorten the bleeding time in rabbits. We have investigated whether infusion of rFVIIa would enhance fibrin formation in bleeding time wounds in patients with thrombocytopenia as reflected by a shortening of the bleeding time. A reduction of the bleeding time was found in 55/105 cases (52%). The decrease was significantly more pronounced when the platelet count exceeded 20 x 10(9)/l. With the exception of an anaphylactoid reaction in 1 patient, no major adverse reactions related to the study drug were observed. Nine infusions of rFVIIa were given to 8 thrombocytopenic patients with overt bleeding. One patient received two infusions. Bleeding decreased in all patients and stopped in 6 patients.

Recombinant activated factor VII in the treatment of bleeding episodes in patients with inherited and acquired bleeding disorders.

The FVIII/FIX by-passing agent, rFVIIa, offers an alternative approach to the treatment of hemophilia patients as well as nonhemophiliacs with antibodies against FVIII/FIX. Such treatment can be administered regardless of the inhibitor titer in these patients, and rFVIIa is active hemostatically in hemophilia B patients also. It is easy to administer but seems to need repeated dosing at 2 to 3-hour intervals, at least initially, in patients with severe bleeding, with a dose of 70 to 100 micrograms/kg body weight required to induce hemostasis. Depending on the severity of the bleeding the dose intervals may be prolonged to every 3 hours for 1 to 2 days or until clinical improvement is observed. Thereafter, the dosage interval can be increased to every 4 hours if continued therapy is required.

Clinical update on the use of recombinant factor VII

Much effort has converged on finding an agent capable of activating the final common pathway of the coagulation cascade inducing hemostasis independently of factor VIII (F.VIII) or factor IX (RIX). Such an agent should be not only hemostatically active but also safe with respect to thromboembolic complications. Factor Vila (F.VIIa) becomes proteolytically active when complexed with tissue factor or other phopholipids minimizing the risk of inducing systemic activation of the coagulation system.

Monoclonal Antibody TB-403: A First-in-Human, Phase I, Double-Blind, Dose Escalation Study Directed Against Placental Growth Factor in Healthy Male Subjects

BACKGROUND TB-403 (RO5323441) is a humanized monoclonal antibody directed against placental growth factor (PlGF). Preclinical studies have demonstrated that targeting PlGF can result in significant inhibition of tumor growth and metastasis. OBJECTIVES The purpose of this study was to assess the safety profile, tolerability, and pharmacokinetics of TB-403, developed for the treatment of solid tumors. METHODS Healthy male subjects were exposed to a single intravenous infusion of TB-403 or placebo. Blood samples for hematology, clinical chemistry, coagulation factors, and urinalysis were collected; vital signs and ECGs were recorded; and serial blood samples were drawn for pharmacokinetic and immunogenicity measurements and circulating levels of pharmacodynamics markers PlGF and (VEGF) vascular endothelial growth factor. Sixteen subjects received either placebo or TB-403 at doses ranging from 0.3 to 5.0 mg/kg. RESULTS Mild (grade 1 or 2) nasopharyngitis, headache, neck pain, and joint pain were the most frequently reported adverse events (AEs). There were no serious AEs in the study, and none of the AEs led to withdrawal. None of the safety laboratory assessments was considered clinically significant, and none was reported as an AE. There were no apparent differences in terms of safety profiles among the 3 dose levels of active treatment compared with placebo. Clearance, volume of distribution, and terminal t(½) (mean values) for TB-403 in all 3 cohorts were in the range of 4.2 to 4.9 (mL/d/kg), 56 to 79 (mL/kg), and 8 to 13 (days), respectively. CONCLUSION The highest dose of TB-403 (5.0 mg/kg) was well tolerated in this study of a single intravenous infusion to healthy males. This result allowed a higher starting dose level in a subsequent Phase I study in cancer patients, the patient population for which this antibody is developed.

Single intravenous administration of TB-402 for the prophylaxis of venous thromboembolism after total knee replacement: a dose-escalating, randomized, controlled trial

Summary.  Background: TB‐402 is a novel anticoagulant monoclonal antibody with a prolonged antithrombotic effect resulting from its partial factor (F)VIII inhibition and long half‐life. We evaluated the efficacy and safety of a single administration of TB‐402 for the prevention of venous thromboembolism (VTE) after total knee replacement (TKR). Patients and methods: This was a phase II, dose‐escalating, randomized, enoxaparin‐controlled, open‐label study. Patients were post‐operatively assigned to a single dose of TB‐402 (0.3, 0.6 or 1.2 mg kg−1) or enoxaparin 40 mg for at least 10 days (n = 75 per group; 3:1 TB‐402 to enoxaparin). The primary efficacy outcome was total VTE defined as asymptomatic deep vein thrombosis (DVT) detected by bilateral venography and symptomatic VTE by day 7 to 11. The principal safety outcome was the incidence of major bleeding and clinically relevant non‐major bleeding. Results: Total VTE was lower in all TB‐402 groups compared with enoxaparin: 16.7%(95% CI 9.8–26.9), 23.9%(95% CI 15.3–35.3), 24.1%(95% CI 16.0–34.5) and 39.0%(95% CI 28.8–50.1) for TB‐402 0.3, 0.6, 1.2 mg kg−1 and enoxaparin, respectively (P = 0.003 for TB‐402 0.3 mg kg−1 vs. enoxaparin). The incidence of total VTE in the pooled TB‐402 groups was 21.6% (95%CI 16.6–27.5), an absolute risk reduction vs. enoxaparin of 17.4% (95% CI 5.2–29.6). Major or clinically relevant non‐major bleeding was observed in 3/75(4.0%), 4/74(5.4%), 7/87(8.0%) and 3/79(3.8%) patients for TB‐402 0.3, 0.6, 1.2 mg kg−1 and enoxaparin, respectively. Conclusions: TB‐402, as a single post‐operative administration, was associated with a lower rate of VTE in all doses tested, compared with enoxaparin. The incidence of major and clinically relevant non‐major bleeding was similar to enoxaparin 40 mg for TB‐402 0.3 and 0.6 mg kg−1.

Tolerability and pharmacokinetics of TB-402 in healthy male volunteers

BACKGROUND TB-402, a human monoclonal antibody that partially inhibits Factor VIII activity (FVIII:C), is being developed as a long-acting antithrombotic agent. OBJECTIVES The primary goal of this study was to investigate the tolerability of TB-402 in healthy male volunteers. Secondary objectives were to determine the pharmacokinetics and pharmacodynamics of TB-402. METHODS In this ascending-dose study, healthy subjects aged 18 to 45 years were randomly assigned in a 2:1 ratio to receive TB-402 administered as a single intravenous bolus at 0.015, 0.1, 0.5, 2.5, 12.5, 37.5, 188, 620, or 1860 microg/kg or matching inactive vehicle (placebo). An older group (55-75 years) was also administered the highest dose that was well tolerated in the younger group (1860 microg/kg). Adverse events (AEs) were obtained from spontaneous reporting and from answers to nonleading questions asked by the principal investigator and study staff during follow-up visits on days 4, 7 (+/-1 day), 14 (+/-1 day), 21 (+/-2 days), 28 (+/-3 days), 42 (+/-3 days), and 56 (+/-3 days) after TB-402 administration. AEs were monitored up to the last study visit on day 56 after the administration of TB-402 or placebo, with special attention to bleeding events. The pharma-codynamic assessment of TB-402 included changes in FVIII:C, activated partial thromboplastin time (APTT), and prothrombin time (PT). RESULTS The study enrolled 56 subjects (mean ages: younger group, 28 years [range, 20-45 years]; older group, 65 years [range, 58-76 years]; weight, 79 kg [range, 60-104 kg] and 81 kg [range, 64-94 kg], re-spectively). Thirty-one of the 38 subjects who received TB-402 (82%) experienced a total of 85 treatment-emergent AEs (TEAEs), and 14 of 18 subjects who received placebo (78%) experienced 35 TEAEs. A total of 34 bleeding events were reported in 13 of 38 subjects (34%) who received TB-402 and 7 of 18 subjects (39%) who received placebo. Most common AEs reported in subjects who received TB-402 were headache (11 [29%]), vessel puncture-site hematoma (7 [18%]), and traumatic hematoma (5 [13%]); with placebo, these AEs were vessel puncture-site hematoma (4 [22%]), headache (3 [17%]), vasovagal reaction (3 [17%]), and hematuria (3 [17%]). No serious AEs considered to be related to TB-402 were reported, and no dose-dependent increases in bleeding events were observed. On pharmacokinetic analysis of TB-402, the t(1/2) values across doses were 22.9 days (age 18-45 years) and 19.5 days (age 55-75 years). TB-402 was associated with a reduction in FVIII:C over a period of approximately 48 hours in the d37.5-microg/kg dose groups. TB-402 was associated with a prolonged APTT at doses >or=2.5 microg/kg approximately 1.1-1.2-fold predose APTT). Administration of a higher dose of TB-402 was associated with an extended duration of APTT prolongation. No significant effect on PT was found. CONCLUSIONS In this study in healthy male volunteers, TB-402 was well tolerated in the population studied. Based on the findings from this study, the long t(1/2) of TB-402 may allow a pharmacodynamic effect over a prolonged period after single-dose administration. Further trials are needed to address the tolerability and efficacy of this agent in preventing thromboembolism. Clinicaltrials.gov identifier: NCT00612196.

PROLONGED RECOMBINANT ACTIVATED FACTOR VII (rFVIIa) TREATMENT FOR SEVERE BLEEDING IN A FACTOR‐IX‐DEFICIENT PATIENT WITH AN INHIBITOR

and a slight increase of LDH from 232 to 294 IU/I. The effect on the platelet count was not correlated with the degree of haemolysis. All our patients with chronic ITP had a persistent increase in their platelet counts to above 60 x 10y/l, and did not require any other specific therapy. Bleeding was reduced in all patients. This uncontrolled study confirms the beneficial effect of dapsone reported in a patient with systemic lupus and thrombocytopenia in which the skin and thrombocytopenic purpura have been controlled for 6 years with no side effects (Moss & Hamilton, 1988). The effect on platelet counts can be maintained over long periods of time. Platelet counts decreased when dapsone was stopped: maintenance therapy may be required. Clinical tolerance was good, except for mild cytolysis in one patient. Sulphones. however, are potentially toxic, but with doses under 300 mg daily toxic reactions to dapsone are uncommon (Lowe, 1950). Most of the reactions are dose related. Some, as dapsone syndrome, leucopenia and agranulocytosis, are idiosyncrasies and usually occur after 2-8 weeks of continuous therapy. although rarely cases may develop after months or years (Graham. 1975). So it appears prudent to measure haemoglobin. platelets, white cell count, and liver function tests at 2-week intervals for the first weeks of therapy. The mechanism by which dapsone induces remission is unknown. Since phagocytosis of autoantibody-coated platelets can efficiently be blocked by infusion of red blood cell stroma (Shulman et al. 1965). excessive red blood cell destruction induced by dapsone may interfere with platelet sequestration by the reticuloendothelial system. In this study the platelet counts without pronounced haemolysis does not corroborate this hypothesis. Absence of a decrease in plateletassociated immunoglobulins after treatment suggested that dapsone does not interfere with binding of serum antiplatelet antibody to platelets. Dapsone affects phagocyte-mediated cytotoxicity (Stendahl et al, 1978), which provides a possible explanation for its beneficial effects in thrombocytopenia. It cannot be overemphasized that the goal of therapy in ITP should not be necessarily directed toward restoration of a normal platelet count, but to increasing the platelet count to a level sufficient for the maintenance of haemostasis for normal daily activity. This can generally be achieved with a platelet count of 40-60 x 10y/l (Karpatkin, 1985), and. to this end. dapsone is an inexpensive therapy which may be useful in elderly patients with ITP. Further trials are needed to confirm the beneficial effect of this agent in ITP.

Abstract A111: A phase I, dose escalation study of TB‐403, a monoclonal antibody directed against PlGF, in patients with solid tumors

Rationale and Objectives: TB‐403 is a humanised recombinant immunoglobulin G isotype 1 monoclonal antibody expressed in Chinese hamster ovary cells and directed to the receptor‐binding site of placental growth factor (PlGF). The antibody is highly specific and does not cross‐react with vascular endothelial growth factor A (VEGFA). PlGF levels are low in normal tissues, but up‐regulated in several pathological conditions, including several types of cancer. TB‐403 has been shown to significantly inhibit tumor growth in xenograft tumor models. The primary objective of the phase 1 study was to determine the maximum tolerated dose (if Methods: In this multi‐center study, cohorts of 3 patients were treated with 8 weekly doses of 1.25, 5, or 10 mg/kg or 3 doses of 20 and 30 mg/kg once every three weeks (q3w). Six additional patients were treated with 30 mg/kg q3W. Patients showing objective tumor response or stable disease (SD) after 8 weeks were offered extended therapy. Main eligible criteria were: solid tumor with no other treatment options, ECOG performance status 0–1, normal organ function, and no prior anticancer therapy within 30 days (bevacizumab within 60 days). Results: A total of 23 patients were accrued. No DLT, changes in ECG, laboratory findings or urine analysis were seen, except for one patient with an unrelated biliary stenoses. Of related or possibly related grade III or IV adverse events only one episode of pulmonary embolism, one case of dyspnoea and a case of dry skin were observed. Related or possibly related grade I and II adverse events included skin rash (1 patient), fatigue (5 patients), fever (1 patient), diarrhoea (1 patient), and hypertension (1 patient). No objective responses according to RECIST criteria were observed but five patients had SD ≥ 8 weeks, including 2 patients (pancreatic adenocarcinoma and esophageal squamous carcinoma) treated with weekly 5 mg/kg TB‐403 with SD > 10 months. Conclusion: TB‐403 was well tolerated. MTD was not established due to lack of dose‐limiting toxicity up to a dose of 10 mg/kg weekly and 30 mg/kg q3w. Prolonged SD (> 10 months) was seen in two patients treated with 5 mg/kg weekly TB‐403. Pharmacokinetic and molecular pharmacodynamic data will be presented. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A111.

Antidote strategies to reverse anticoagulation with TB-402, a long-acting partial inhibitor of factor VIII

Summary.  Background:  TB‐402 is a partially inhibiting antibody of factor VIII that is under development as a long‐acting anticoagulant.

Abstract A3: A first‐in‐man, phase I, dose escalation study of TB‐403, a monoclonal antibody directed against PlGF, in healthy male subjects

Rationale and Objectives: TB‐403 is a humanised recombinant immunoglobulin G isotype 1 (IgG1) monoclonal antibody expressed in Chinese hamster ovary (CHO) cells and directed to the receptor‐binding site of placental growth factor (PlGF). The antibody is highly specific and does not cross‐react with vascular endothelial growth factor (VEGF). Whilst VEGF is involved both in physiological and pathological angiogenesis, the levels of PlGF are low in normal tissues, but up‐regulated in several pathological conditions, including several types of cancer. TB‐403 has been shown to significantly inhibit tumor growth in xenograft tumor models. In all preclinical studies performed with TB‐403 there were no drug‐related findings up to and including the maximum feasible doses tested (300 mg/kg/wk IV in the cynomolgus monkey for 13 weeks). This first‐in‐man (FIM) study was designed to investigate the safety and tolerability of a single dose of TB‐403 in healthy male subjects. A secondary objective included the investigation of the single dose pharmacokinetics of TB‐403. Methods: This FIM study was a phase 1, double‐blind, randomized, placebo‐controlled, single‐dose escalation study in healthy male subjects. Sixteen male subjects in 3 dose groups were exposed to a single, intravenous infusion of TB‐403 or placebo over 60 minutes at dose levels of 0.3, 1.25 or 5.0 mg/kg with 2+2, 4+2 and 4+2 subjects per group, respectively. The starting dose was selected as 1/10th of the Minimum Anticipated Biological Effect Level (MABEL) determined in a xenograft tumor model. TB‐403 was given at escalating doses and safety was closely monitored up to Day 56. Review of adverse events, safety laboratory results, electrocardiogram and vital sign measurements up to and including Day 7 was performed by a Data Monitoring Committee before dose escalation. Results: All 16 subjects were Caucasians with the age, body weight, and body mass index range of 22–46 years, 63.1–114.5 kg and 20.4–31.4 kg/m2, respectively. The most frequently reported adverse events were nasopharyngitis, headache, neck pain and joint pain with no significant difference in frequency or severity between TB‐403 and placebo for these or other reported adverse events. The adverse events were either not related or unlikely related to TB‐403 and 16 were mild, 8 moderate and 3 severe in intensity. There were no serious adverse events, and none of the events led to withdrawal. Pharmacokinetic properties of TB‐403 were investigated and showed a terminal half‐life of TB‐403 ranging from 8 to 13 days and a dose-proportional exposure in terms of both Cmax and AUC. Conclusion: TB‐403 was safely administered to healthy males in this study without dose‐limiting toxicity after an intravenous infusion in the dose range of 0.3 mg/kg to 5.0 mg/kg. The safe administration of TB‐403 to healthy male subjects allowed a higher initial safe start dose level in a subsequent study in cancer patients. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A3.