Chronic DLL4 blockade induces vascular neoplasms.

Delta-like 4 (DLL4)-mediated Notch signalling has emerged as an attractive target for cancer therapy. However, the potential side effects of blocking this pathway remain uncertain. Here we show that chronic DLL4 blockade causes pathological activation of endothelial cells, disrupts normal organ homeostasis and induces vascular tumours, raising important safety concerns.

Immunogenicity/hypersensitivity of biologics.

This continuing education course was designed to provide an overview of the immunologic mechanisms involved in immunogenicity and hypersensitivity reactions following administration of biologics in nonclinical toxicity studies, the methods used to determine whether such reactions are occurring, and the associated clinical and anatomic pathology findings. Hypersensitivity reactions have classically been divided into type I, II, III, and IV reactions; type I and III reactions are those most often observed following administration of biologics. A variety of methods can be used to detect these reactions. Antemortem methods include hematology; detection of antidrug antibodies, circulating immune complexes and complement fragments, and immunoglobulin E in serum; tests for serum complement activity; and evaluation of complement receptor 1 on erythrocytes. Postmortem methods include routine light microscopy and electron microscopy, which can demonstrate typical findings associated with hypersensitivity reactions, and immunohistochemistry, which can detect the presence of immune complexes in tissues, including the detection of the test article. A final determination of whether findings are related to a hypersensitivity reaction in individual animals or across the entire study should rely on the overall weight of evidence, as findings indicative of these reactions are not necessarily consistent across all affected animals.

Effect of intravitreal injection of ranibizumab in combination with verteporfin PDT on normal primate retina and choroid.

PURPOSE: To evaluate the effect of intravitreal injection of a monoclonal antibody fragment (ranibizumab, also known as rhuFab V2 and Lucentis; Genentech, S. San Francisco, CA) directed against vascular endothelial growth factor (VEGF) in combination with verteporfin photodynamic therapy (PDT) on normal primate retina and choroid. METHODS: Eight cynomolgus monkeys were treated with intravitreal ranibizumab in one eye and placebo in the other, alternating with verteporfin PDT in both eyes on a weekly basis for 6 to 7 weeks. Treatment effects were evaluated by color fundus photography, fluorescein angiography, and light and electron microscopy. RESULTS: Over the course of the study, increasing retinal pigment epithelial changes, with corresponding window defects, developed in both eyes of all animals on fluorescein angiography over the course of the study. No complications attributable to the intravitreal injection of ranibizumab were observed. Histologic analysis revealed a similar reduction in choriocapillaris density in the irradiated area of eyes treated with PDT alone compared with those that received combination treatment. CONCLUSIONS: In this limited study of normal monkey eyes, no severe adverse effects from the combination of intravitreal ranibizumab and verteporfin PDT were demonstrated compared with PDT alone.

Balancing Efficacy and Safety of an Anti-DLL4 Antibody through Pharmacokinetic Modulation.

PURPOSE: Although agents targeting Delta-like ligand 4 (DLL4) have shown great promise for angiogenesis-based cancer therapy, findings in recent studies have raised serious safety concerns. To further evaluate the potential for therapeutic targeting of the DLL4 pathway, we pursued a novel strategy to reduce toxicities related to DLL4 inhibition by modulating the pharmacokinetic (PK) properties of an anti-DLL4 antibody. EXPERIMENTAL DESIGN: The F(ab')2 fragment of anti-DLL4 antibody (anti-DLL4 F(ab')2) was generated and assessed in efficacy and toxicity studies. RESULTS: Anti-DLL4 F(ab')2 enables greater control over the extent and duration of DLL4 inhibition, such that intermittent dosing of anti-DLL4 F(ab')2 can maintain significant antitumor activity while markedly mitigating known toxicities associated with continuous pathway inhibition. CONCLUSIONS: PK modulation has potentially broad implications for development of antibody-based therapeutics. Our safety studies with anti-DLL4 F(ab')2 also provide new evidence reinforcing the notion that the DLL4 pathway is extremely sensitive to pharmacologic perturbation, further underscoring the importance of exercising caution to safely harness this potent pathway in humans.

Safety and efficacy of intravitreal injection of ranibizumab in combination with verteporfin PDT on experimental choroidal neovascularization in the monkey.

OBJECTIVE: To study the safety and efficacy of intravitreal injections of anti-vascular endothelial growth factor antibody fragment (ranibizumab [formerly known as rhuFabV2], Lucentis; Genentech, South San Francisco, Calif) in combination with intravenous verteporfin (Visudyne; Novartis, East Hanover, NJ) photodynamic therapy (PDT) on experimental choroidal neovascularization in the monkey eye. METHODS: Choroidal neovascularization was induced by laser injury in both eyes of cynomolgus monkeys and followed with weekly fundus photography and fluorescein angiography. Two weeks after induction, weekly treatments were initiated. These treatments included using either an intravitreal injection of ranibizumab (previously known as rhuFabV2) in combination with verteporfin PDT or a ranibizumab vehicle (placebo) in combination with verteporfin PDT (PDT only). Six animals (group 1) initially received intravitreal injections followed 1 week later by PDT. Four animals (group 2) initially received PDT followed 1 week later by intravitreal injection. Two animals (group 3) received injections and PDT on the same day at 2-week intervals. Photodynamic therapy was applied in all 3 groups every 2 weeks for 3 treatments with follow-up through 2 weeks after the last PDT treatment. Fluorescein angiograms were graded using a masked standardized protocol. The data were analyzed using the McNemar chi(2) test for matched pairs. RESULTS: No choroidal neovascularization leakage was observed in the eyes of animals treated with ranibizumab and PDT at day 21 or 42 after the start of the first treatment. Leakage persisted in eyes treated with PDT alone at 21 days (3 of 12 eyes) and 42 days (2 of 12 eyes). At all time points studied, the ranibizumab and PDT-treated eyes experienced better angiographic outcomes than the eyes receiving PDT alone. CONCLUSION: These preliminary data indicate that an intravitreal ranibizumab injection in combination with verteporfin PDT (ranibizumab and PDT) causes a greater reduction in angiographic leakage than PDT and intravitreal vehicle injection (PDT only) in experimental choroidal neovascularization. CLINICAL RELEVANCE: This combination therapy can potentially offer a new treatment modality for choroidal neovascularization in patients with macular degeneration and other diseases.

A Phase Ib study evaluating MNRP1685A, a fully human anti-NRP1 monoclonal antibody, in combination with bevacizumab and paclitaxel in patients with advanced solid tumors.

PURPOSE: MNRP1685A is a human monoclonal antibody that blocks binding of vascular endothelial growth factor (VEGF), VEGF-B, and placental growth factor 2 to neuropilin-1 resulting in vessel immaturity and VEGF dependency. The safety of combining MNRP1685A with bevacizumab, with or without paclitaxel, was examined. METHODS: Patients with advanced solid tumors received escalating doses of MNRP1685A (7.5, 15, 24, and 36 mg/kg) with bevacizumab 15 mg/kg every 3 weeks in Arm A (n = 14). Arm B (n = 10) dosing consisted of MNRP1685A (12 and 16 mg/kg) with bevacizumab 10 mg/kg (every 2 weeks) and paclitaxel 90 mg/m(2) (weekly, 3 of 4 weeks). Objectives were to determine safety, pharmacokinetics, pharmacodynamics, and the maximum tolerated dose of MNRP1685A. RESULTS: Infusion reactions (88 %) and transient thrombocytopenia (67 %) represent the most frequent study drug-related adverse events (AEs). Drug-related Grade 2 or 3 proteinuria occurred in 13 patients (54 %). Additional study drug-related AEs occurring in >20 % of patients included neutropenia, alopecia, dysphonia, fatigue, and nausea. Neutropenia occurred only in Arm B. Grade ≥3 study drug-related AEs in ≥3 patients included neutropenia (Arm B), proteinuria, and thrombocytopenia. Two confirmed and three unconfirmed partial responses were observed. CONCLUSIONS: The safety profiles were consistent with the single-agent profiles of all study drugs. However, a higher than expected rate of clinically significant proteinuria was observed that does not support further testing of MNRP1685A in combination with bevacizumab.

Developmental immunotoxicology assessment of rituximab in cynomolgus monkeys.

Rituximab is a chimeric murine/human-engineered immunoglobulin (Ig) G1 anti-CD20 monoclonal antibody, selectively depleting CD20-expressing cells in peripheral blood and lymphoid tissues. As part of the rituximab registration-enabling program for rheumatoid arthritis, cynomolgus monkey embryo-fetal development and pre- and postnatal developmental toxicity studies were performed. In both studies, female cynomolgus monkeys were administered rituximab iv at doses of 0/0, 15/20, 37.5/50, and 75/100 mg/kg (loading dose/study dose) from gestation day (GD) 20 to 50 for the embryo-fetal development study and GD 20 to postpartum (pp) day 28 for the pre- and postnatal study. In the embryo-fetal development study, although maternal dosing ended during the first trimester at GD 50, placental transfer of rituximab to fetuses was demonstrated at GD 100. Consequently, fetuses demonstrated B-cell depletion in lymphoid tissues at GD 100. Repletion of B cells was demonstrated in infants in a follow-up pre- and postnatal study following fetal and neonatal exposure. In the pre- and postnatal study, despite B-cell depletion, there was no significant functional consequence on the infant's ability to mount T-cell-dependent antibody responses following vaccination or antigenic challenge. Overall, rituximab was well tolerated at maximum feasible doses up to 100 mg/kg in pregnant cynomolgus monkeys and their infants after exposure from the period of organogenesis throughout pregnancy, parturition, and postnatal development. Importantly, the preclinical data have been concordant with the clinical data in children for cases where rituximab was administered during pregnancy.

Pharmacokinetics and retinal distribution of ranibizumab, a humanized antibody fragment directed against VEGF-A, following intravitreal administration in rabbits.

PURPOSE: Ranibizumab (Lucentis) is a humanized antigen-binding fragment designed to inhibit all isoforms and active degradation products of vascular endothelial growth factor A (VEGF-A); it is in clinical development for the treatment of neovascular age-related macular degeneration (AMD). This study evaluated its pharmacokinetics (PK) and retinal distribution in rabbits when administered intravitreally (ITV). METHODS: A total of 27 New Zealand white rabbits received a single bilateral ITV injection of ranibizumab 625 muicrog/eye (Group 1, n = 24) or I-labeled ranibizumab 625 microg/eye, 22.5 microCi/eye (Group 2, n = 3). Ranibizumab concentration was determined in the vitreous, aqueous humor, and serum up to 60 days postdose by enzyme-linked immunosorbent assay in Group 1. Group 2 eyes were microautoradiographed on days 1-4. RESULTS: Ranibizumab has a terminal half-life of 2.9 days in the ocular compartments. Systemic exposure was low, measuring less than 0.01% of vitreous exposure when comparing AUC0-t values. Microautoradiography analysis demonstrated that ranibizumab penetrated all retinal layers, reaching the choriocapillaris on days 1, 2, and 4. CONCLUSIONS: This study demonstrates that following ITV injection, ranibizumab has a vitreous half-life of 2.9 days with minimal systemic exposure. Ranibizumab rapidly penetrates through the retina to reach the choroid, supporting its clinical development for neovascular AMD.