Pharmacokinetics of Ranibizumab after Intravitreal Administration in Patients with Retinal Vein Occlusion or Diabetic Macular Edema

Population Pharmacokinetics of Ranibizumab Delivered via the Port Delivery System Implanted in the Eye in Patients with Neovascular Age-Related Macular Degeneration

The port delivery system with ranibizumab (PDS) is designed to continuously deliver ranibizumab to maintain therapeutic drug concentrations in the vitreous of the eye for an extended duration. The PDS has been evaluated for the treatment of neovascular age-related macular degeneration in the Ladder (PDS 10, 40, and 100 mg/mL, with refill exchanges as needed, versus monthly intravitreal ranibizumab 0.5 mg), Archway (PDS 100 mg/mL with 24-week refill exchanges, versus monthly intravitreal ranibizumab 0.5 mg), and ongoing Portal (PDS 100 mg/mL with 24-week refill exchanges) clinical trials. Data from Ladder, Archway, and Portal were used to develop a population pharmacokinetics (PK) model to estimate the ranibizumab release rate from the PDS implant, describe ranibizumab PK in serum and aqueous humor, and predict the concentration in vitreous humor. A model was developed to adequately describe the serum and aqueous humor PK data, as suggested by goodness-of-fit plots as well as visual predictive checks. In the final model, the first-order implant release rate was estimated to be 0.00654 (1/day), corresponding to a half-life of 106 days, consistent with the implant release rate determined in vitro. The model-predicted vitreous concentrations achieved with PDS 100 mg/mL given every 24 weeks were below the intravitreal peak concentration and above the intravitreal trough concentration of ranibizumab over the entire 24-week refill interval. The results demonstrate a durable release of ranibizumab from the PDS with a half-life of 106 days, providing vitreous exposure to ranibizumab for at least 24 weeks that is within the range of exposure for monthly intravitreal treatment.

Systemic exposure following intravitreal administration of therapeutic agents: an integrated pharmacokinetic approach. 1. THR-149

Intravitreal (IVT) injection of pharmacological agents is an established and widely used procedure for the treatment of many posterior segment of the eye diseases. IVT injections permit drugs to reach high concentrations in the retina whilst limiting systemic exposure. Beyond the risk of secondary complications such as intraocular infection, the potential of systemic adverse events cannot be neglected. Therefore, a detailed understanding of the rules governing systemic exposure following IVT drug administration remains a prerequisite for the evaluation and development of new pharmacological agents intended for eye delivery. We present here a novel mathematical model to describe and predict circulating drug levels following IVT in the rabbit eye, a species which is widely used for drug delivery, pharmacokinetic, and pharmacodynamic studies. The mathematical expression was derived from a pharmacokinetic model that assumes the existence of a compartment between the vitreous humor compartment itself and the systemic compartment. We show that the model accurately describes circulating levels of THR-149, a plasma kallikrein inhibitor in development for the treatment of diabetic macular edema. We hypothesize that the model based on the rabbit eye has broader relevance to the human eye and can be used to analyze systemic exposure of a variety of drugs delivered in the eye.

Systemic exposure following intravitreal administration of therapeutic agents: an integrated pharmacokinetic approach. 2. THR-687

Intravitreal (IVT) injection remains the preferred administration route of pharmacological agents intended for the treatment of back of the eye diseases such as diabetic macular edema (DME) and neovascular age-related macular degeneration (nvAMD). The procedure enables drugs to be delivered locally at high concentrations whilst limiting whole body exposure and associated risk of systemic adverse events. Nevertheless, intravitreally-delivered drugs do enter the general circulation and achieving an accurate understanding of systemic exposure is pivotal for the evaluation and development of drugs administered in the eye. We report here the full pharmacokinetic properties of THR-687, a pan RGD integrin antagonist currently in clinical development for the treatment of DME, in both rabbit and minipig. Pharmacokinetic characterization included description of vitreal elimination, of systemic pharmacokinetics, and of systemic exposure following IVT administration. For the latter, we present a novel pharmacokinetic model that assumes clear partition between the vitreous humor compartment itself where the drug is administered and the central systemic compartment. We also propose an analytical solution to the system of differential equations that represent the pharmacokinetic model, thereby allowing data analysis with standard nonlinear regression analysis. The model accurately describes circulating levels of THR-687 following IVT administration in relevant animal models, and we suggest that this approach is relevant to a range of drugs and analysis of subsequent systemic exposure.

Ranibizumab for the treatment of diabetic retinopathy

Introduction: Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus and the leading cause of blindness in young adults. Prior to anti-vascular endothelial growth factor (anti-VEGF) agents, the treatment of DR was based on control of systemic factors and laser photocoagulation. Over the past decade, the use of anti-VEGF agents has revolutionized the treatment of DR, including diabetic macular edema (DME).Areas covered: Ranibizumab has been proven to be effective for the treatment of DME in large clinical trials, while patients in these studies have been assessed in terms of DR severity change. In this review, evidence from randomized trials regarding the use of ranibizumab for DR treatment is presented.Expert opinion: A comprehensive presentation of randomized clinical trials evaluating ranibizumab for DR indicates that it is effective and safe, offering improvement of DR severity in both non-proliferative and proliferative forms. However, there is no general consensus regarding the exact treatment regimen in patients with DR, while the effect of ranibizumab on the progression of retinal ischemia remains unclear.

Sustained suppression of VEGF for treatment of retinal/choroidal vascular diseases

Neovascular age-related macular degeneration (NVAMD) is the most prevalent choroidal vascular disease, and diabetic retinopathy (DR) and retinal vein occlusion (RVO) are the most prevalent retinal vascular diseases. In each of these, hypoxia plays a central role by stabilizing hypoxia-inducible factor-1 which increases production of vascular endothelial growth factor (VEGF) and other hypoxia-regulated gene products. High VEGF causes excessive vascular permeability, neovascularization, and in DR and RVO, promotes closure of retinal vessels exacerbating hypoxia and creating a positive feedback loop. Hence once VEGF expression is elevated it tends to remain elevated and drives disease progression. While other hypoxia-regulated gene products also contribute to pathology in these disease processes, it is remarkable how much pathology is reversed by selective inhibition of VEGF. Clinical trials have demonstrated outstanding visual outcomes in patients with NVAMD, DR, or RVO from frequent intraocular injections of VEGF-neutralizing proteins, but for a variety of reasons injection frequency has been substantially less in clinical practice and visual outcomes are disappointing. Herein we discuss the rationale, preclinical, and early clinical results of new approaches that provide sustained suppression of VEGF. These approaches will revolutionize the management of these prevalent retinal/choroidal vascular diseases.

A review on vasohibin and ocular neovascularization

Ischemic and neovascular disease is one of the most difficult ocular diseases to deal with nowadays. Redundancy, poor visual acuity and decreased life quality are bothering patients and ophthalmologists for decades. After vascular endothelial growth factor (VEGF) was found to be a primary factor in promoting retinal angiogenesis, intravitreal injection of anti-VEGF drugs has been the first-line treatment. Whereas, some patients are refractory to this therapy and problems of economic burden, local complications and adverse effects promote researches into other possible targets. The vasohibin (VASH) family is a newly-investigated factor in modulating ocular angiogenesis. The family includes VASH1 and VASH2, which show opposite effects of inhibiting and accelerating angiogenesis respectively. Positive results have been reported in cellular and animal experiments. With further researches, it can be a promising future target of treating ocular neovascular diseases.

Ocular Half-Life of Intravitreal Biologics in Humans and Other Species: Meta-Analysis and Model-Based Prediction

Therapeutic antibodies administered intravitreally are the current standard of care to treat retinal diseases. The ocular half-life (t_1/2) is a key determinant of the duration of target suppression. To support the development of novel, longer-acting drugs, a reliable determination of t_1/2 is needed together with an improved understanding of the factors that influence it. A model-based meta-analysis was conducted in humans and nonclinical species (rat, rabbit, monkey, and pig) to determine consensus values for the ocular t_1/2 of IgG antibodies and Fab fragments. Results from multiple literature and in-house pharmacokinetic studies are presented within a mechanistic framework that assumes diffusion-controlled drug elimination from the vitreous. Our analysis shows, both theoretically and experimentally, that the ocular t_1/2 increases in direct proportion to the product of the hydrodynamic radius of the macromolecule (3.0 nm for Fab and 5.0 nm for IgG) and the square of the radius of the vitreous globe, which varies approximately 24-fold from the rat to the human. Interspecies differences in the proportionality factors are observed and discussed in mechanistic terms. In addition, mathematical formulae are presented that allow prediction of the ocular t_1/2 for molecules of interest. The utility of these formulae is successfully demonstrated in case studies of aflibercept, brolucizumab, and PEGylated Fabs, where the predicted ocular t_1/2 values are found to be in reasonable agreement with the experimental data available for these molecules.

A new era for migraine: Pharmacokinetic and pharmacodynamic insights into monoclonal antibodies with a focus on galcanezumab, an anti-CGRP antibody

PURPOSE

To review pharmacokinetic and pharmacodynamic characteristics of antibodies that bind to soluble ligands within the framework of calcitonin gene-related peptide antibodies.

OVERVIEW

Calcitonin gene-related peptide has been implicated in the pathophysiology of migraine. Galcanezumab is an antibody that binds to the ligand calcitonin gene-related peptide. Other antibodies that target calcitonin gene-related peptide include eptinezumab and fremanezumab. To understand how antibodies can affect the extent and duration of free ligand concentrations, it is important to consider the dose and pharmacokinetics of an antibody, and the kinetics of the ligand and antibody-ligand complex. Insights regarding the pharmacokinetic/pharmacodynamic properties of galcanezumab as a probe antibody drug and calcitonin gene-related peptide as its binding ligand regarding its clinical outcomes are provided.

DISCUSSION

Antibodies are administered parenterally because oral absorption is limited by gastrointestinal degradation and inefficient diffusion through the epithelium. The systemic absorption of antibodies following intramuscular or subcutaneous administration most likely occurs via convective transport through lymphatic vessels into blood. The majority of antibody elimination occurs via intracellular catabolism into peptides and amino acids following endocytosis. Binding of ligand to an antibody reduces the free ligand that is available to interact with the receptor and efficacy is driven by the magnitude and duration of the reduction in free ligand concentration. A galcanezumab pharmacokinetic/pharmacodynamic model shows that galcanezumab decreases free calcitonin gene-related peptide concentrations in a dose- and time-dependent manner and continues to suppress free calcitonin gene-related peptide with repeated dosing. The model provides evidence for a mechanistic linkage to galcanezumab therapeutic effects for the preventive treatment of migraine.

Pharmacokinetics of Intravitreal Anti-VEGF Drugs in Age-Related Macular Degeneration

Intravitreal administration of anti-vascular endothelial growth factor (VEGF) antibodies has become the standard treatment for Age-Related Macular Degeneration; however, the knowledge of their pharmacokinetics is limited. A comprehensive review of the preclinical and clinical pharmacokinetic data that were obtained in different studies with intravitreal bevacizumab, ranibizumab, and aflibercept has been conducted. Moreover, the factors that can influence the vitreous pharmacokinetics of these drugs, as well as the methods that were used in the studies for analytical determination, have been exposed. These anti-VEGF drugs present different charge and molecular weights, which play an important role in vitreous distribution and elimination. The pharmacokinetic parameters that were collected differ depending on the species that were involved in the studies and on physiological and pathological conditions, such as vitrectomy and lensectomy. Knowledge of the intravitreal pharmacokinetics of the anti-VEGF drugs that were used in clinical practice is of vital importance.

Risk of Systemic Adverse Events Associated with Intravitreal Anti-VEGF Therapy for Diabetic Macular Edema in Routine Clinical Practice

PURPOSE

Intravitreal anti-vascular endothelial growth factor (VEGF) pharmacotherapy has become standard of care for the management of diabetic macular edema (DME). The systemic safety profile of this treatment in routine clinical practice remains incompletely understood. We used a large claims database to investigate the risk of systemic serious adverse events (SAEs) in patients receiving anti-VEGF for DME compared with controls treated with macular laser photocoagulation or intravitreal corticosteroid.

DESIGN

Retrospective cohort study.

PARTICIPANTS

By using a large U.S. insurance database, we identified privately insured and Medicare Advantage patients aged ≥18 years treated with anti-VEGF for DME between January 1, 2006, and December 31, 2015, along with control patients receiving macular laser or corticosteroid. We included patients with 1 year of medical coverage before initial DME treatment.

METHODS

We assessed associations between treatment modalities and predefined systemic outcomes using Cox proportional hazards regression. We performed 2 separate comparisons, one between anti-VEGF and macular laser and one between anti-VEGF and corticosteroid. We used inverse propensity score weighting for the first comparison to account for treatment selection bias. For the second, we used 2:1 propensity score matching on demographics, year, and baseline comorbidities because of the smaller number of corticosteroid-treated patients.

MAIN OUTCOME MEASURES

Risk of cerebrovascular disease, myocardial infarction, major bleeding, and all-cause hospitalization occurring within 6 months of initial DME treatment as hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS

A total of 23 348 patients receiving treatment for DME met inclusion criteria; 13 365 received macular laser, 9219 received intravitreal anti-VEGF, and 764 received intravitreal corticosteroid as initial treatment. Anti-VEGF pharmacotherapy was not associated with an increased hazard of cerebrovascular disease (HR, 0.96; 95% CI, 0.65-1.41; P = 0.83), major bleeding (HR, 1.23; 95% CI, 0.76-1.99; P = 0.41), or myocardial infarction (HR, 1.03; 95% CI, 0.73-1.44; P = 0.88) when compared with macular laser for DME; however, there was an increased hazard of post-treatment all-cause hospital admission (HR, 1.17; 95% CI, 1.05-1.30; P = 0.01). The rates of all primary systemic SAE outcomes were similar after treatment with anti-VEGF versus corticosteroid (P > 0.05 for all).

CONCLUSIONS

We identified no increased risk of cerebrovascular disease, myocardial infarction, or major bleeding within 6 months after intravitreal anti-VEGF pharmacotherapy for the treatment of DME in routine clinical practice. A potential difference in all-cause hospitalization may merit further investigation.

The reactivation time in the treatment of AMD: a forgotten key parameter?

OBJECTIVE

Summarize and compare the available evidence on the reactivation times in patients with age-related macular degeneration treated with Ranibizumab (RNB).

METHOD

Systematic review of studies that reported the reactivation time of patients (direct method) or the number of injections received in a certain period of follow-up (indirect method).

RESULTS

Only 18 of 89 selected studies reported the average reactivation time of patients in a manifest form, without the need of any calculation. The average calculated, weighted reactivation time was 101.8 days with the direct method and 99.8 days in the indirect method (84 studies included). With both methods, it was found that the average reactivation time of the RCTs was between 2 and 3 weeks less than the average time identified in the observational studies. These differences are also reflected in the clinical results, there being a correlation between the number of doses received and the change in BCVA. The analysis of 11 comparative studies showed a difference in reactivation times between patients treated with RNB or Bevacizumab (BVZ).

CONCLUSION

There are few direct studies of reactivation time, but calculation from the PRN dose number turns out to be a good approximation for retrospective study of the variable. The use of the PRN, with criteria not based on optical coherence tomography scans, delays the application of doses between 2 or 3 weeks, and patients suffer loss of clinical benefits. RNB enables patients to receive less injections than BVZ throughout treatment.

Plasma Vascular Endothelial Growth Factor Concentrations after Intravitreous Anti-Vascular Endothelial Growth Factor Therapy for Diabetic Macular Edema

PURPOSE

To assess systemic vascular endothelial growth factor (VEGF)-A levels after treatment with intravitreous aflibercept, bevacizumab, or ranibizumab.

DESIGN

Comparative-effectiveness trial with participants randomly assigned to 2 mg aflibercept, 1.25 mg bevacizumab, or 0.3 mg ranibizumab after a re-treatment algorithm.

PARTICIPANTS

Participants with available plasma samples (N = 436).

METHODS

Plasma samples were collected before injections at baseline and 4-week, 52-week, and 104-week visits. In a preplanned secondary analysis, systemic-free VEGF levels from an enzyme-linked immunosorbent assay were compared across anti-VEGF agents and correlated with systemic side effects.

MAIN OUTCOME MEASURES

Changes in the natural log (ln) of plasma VEGF levels.

RESULTS

Baseline free VEGF levels were similar across all 3 groups. At 4 weeks, mean ln(VEGF) changes were -0.30±0.61 pg/ml, -0.31±0.54 pg/ml, and -0.02±0.44 pg/ml for the aflibercept, bevacizumab, and ranibizumab groups, respectively. The adjusted differences between treatment groups (adjusted confidence interval [CI]; P value) were -0.01 (-0.12 to +0.10; P = 0.89), -0.31 (-0.44 to -0.18; P < 0.001), and -0.30 (-0.43 to -0.18; P < 0.001) for aflibercept-bevacizumab, aflibercept-ranibizumab, and bevacizumab-ranibizumab, respectively. At 52 weeks, a difference in mean VEGF changes between bevacizumab and ranibizumab persisted (-0.23 [-0.38 to -0.09]; P < 0.001); the difference between aflibercept and ranibizumab was -0.12 (P = 0.07) and between aflibercept and bevacizumab was +0.11 (P = 0.07). Treatment group differences at 2 years were similar to 1 year. No apparent treatment differences were detected at 52 or 104 weeks in the cohort of participants not receiving injections within 1 or 2 months before plasma collection. Participants with (N = 9) and without (N = 251) a heart attack or stroke had VEGF levels that appeared similar.

CONCLUSIONS

These data suggest that decreases in plasma free-VEGF levels are greater after treatment with aflibercept or bevacizumab compared with ranibizumab at 4 weeks. At 52 and 104 weeks, a greater decrease was observed in bevacizumab versus ranibizumab. Results from 2 subgroups of participants who did not receive injections within at least 1 month and 2 months before collection suggest similar changes in VEGF levels after stopping injections. It is unknown whether VEGF levels return to normal as the drug is cleared from the system or whether the presence of the drug affects the assay's ability to accurately measure free VEGF. No significant associations between VEGF concentration and systemic factors were noted.

SYSTEMIC PHARMACOKINETICS AND PHARMACODYNAMICS OF INTRAVITREAL AFLIBERCEPT, BEVACIZUMAB, AND RANIBIZUMAB

After monthly intravitreal injections, the systemic exposures of aflibercept, bevacizumab, and ranibizumab were distinct and correlated with different reductions in plasma free–vascular endothelial growth factor, which could provide biologic plausibility for potential differences in systemic adverse events.

Purpose:

To evaluate the systemic pharmacokinetics (PKs) of aflibercept, bevacizumab, and ranibizumab in patients with neovascular age-related macular degeneration (AMD), diabetic macular edema (DME), or retinal vein occlusion (RVO).

Methods:

Prospective, open-label, nonrandomized clinical trial of patients with AMD, DME, or RVO who were antivascular endothelial growth factor (VEGF) naïve or had not received anti-VEGF for ≥4 months. Patients received 3 monthly intravitreal injections of aflibercept 2.0 mg, bevacizumab 1.25 mg, or ranibizumab (0.5 mg for AMD/RVO, 0.3 mg for DME). The main outcome measures were serum PKs and plasma free-VEGF concentrations after the first and third injections.

Results:

A total of 151 patients were included. In AMD/DME/RVO, systemic exposure to each drug was highest with bevacizumab, then aflibercept, and lowest with ranibizumab. Ranibizumab cleared from the bloodstream more quickly than bevacizumab or aflibercept. Aflibercept treatment resulted in the greatest reductions in plasma free-VEGF relative to baseline levels, whereas ranibizumab treatment resulted in the smallest decreases in plasma free-VEGF.

Conclusion:

The three anti-VEGF treatments examined in this analysis demonstrated notable differences in systemic PKs. Generally, the reduction in plasma free-VEGF levels correlated with elevated levels of circulating anti-VEGF agents, with the reduction in free-VEGF levels greatest with aflibercept and least with ranibizumab.

Effect of intravitreal ranibizumab on the ocular circulation of the untreated fellow eye

Purpose

To evaluate the effects of unilateral intravitreal ranibizumab (IVR) on the ocular circulation of the fellow eyes.

Methods

Fifteen eyes of 15 patients with macular edema (average age 69.6 ± 11.8 years) were studied. Eleven eyes had diabetic macular edema (DME) and four eyes had macular edema associated with a branch retinal vein occlusion. Each eye received 0.5 mg of IVR. The blood circulation on the optic nerve head of the treated and untreated eyes were determined by laser speckle flowgraphy (LSFG, Softcare Co., Ltd) before, 1 day, and 1 week after the IVR. The mean blur rate (MBR) and the relative changes of the MBRs determined as dMBR(%) = 100−(MBR before/MB after) × 100) were evaluated. The central macular thickness (CMT) and the rate of reduction in the thickness (dCMT = 100−(CMT before/CMT after) × 100) were also evaluated.

Results

The mean dMBR was significantly higher in the treated eyes than the untreated eyes at 1 day (−16.4 ± 17.0% vs 2.31 ± 19.3%) and at 1 week (−12.0 ± 14.6% vs 4.50 ± 25.9%) after the IVR (P = 0.02, paired t tests).

Conclusion

These findings indicate that if ranibizumab enters the systemic circulation, the concentration is not high enough to affect the ocular circulation of the fellow eyes.

Drug Development of Therapeutic Monoclonal Antibodies

Monoclonal antibodies (MAbs) have become a substantial part of many pharmaceutical company portfolios. However, the development process of MAbs for clinical use is quite different than for small-molecule drugs. MAb development programs require careful interdisciplinary evaluations to ensure the pharmacology of both the MAb and the target antigen are well-understood. Selection of appropriate preclinical species must be carefully considered and the potential development of anti-drug antibodies (ADA) during these early studies can limit the value and complicate the performance and possible duration of preclinical studies. In human studies, many of the typical pharmacology studies such as renal or hepatic impairment evaluations may not be needed but the pharmacokinetics and pharmacodynamics of these agents is complex, often necessitating more comprehensive evaluation of clinical data and more complex bioanalytical assays than might be used for small molecules. This paper outlines concerns and strategies for development of MAbs from the early in vitro assessments needed through preclinical and clinical development. This review focuses on how to develop, submit, and comply with regulatory requirements for MAb therapeutics.

Aflibercept for the treatment of diabetic macular edema

Diabetic macular edema (DME) is an accumulation of fluid in the central retina, secondary to vascular-leakage from diabetic vascular damage. DME and other ophthalmic sequela of diabetes are the leading cause of blindness in 20 to 74-year-olds. The development of VEGF-inhibitors (anti-VEGF) has revolutionized DME treatment improving the clinician's ability to remove excess fluid from the macula, improving visual-acuity. Aflibercept is an anti-VEGF agent made of a recombinant fusion protein (consisting of VEGF receptors 1 and 2 extracellular domains) fused with the Fc-portion of human-IgG1, which binds both VEGF isoforms A and B, and placental growth factor. Phase III clinical trials and published scientific studies have demonstrated the efficacy of intravitreal aflibercept injection in the treatment of DME.

Ranibizumab: A Review of Its Use in the Treatment of Diabetic Retinopathy in Patients With Diabetic Macular Edema

Objective: To evaluate the pharmacotherapy role of ranibizumab, a vascular endothelial growth factor (VEGF) inhibitor, for the treatment of diabetic retinopathy (DR) in patients with diabetic macular edema (DME). Data Sources: PubMed, Science Direct, Google Scholar, and ClinicalTrials.gov searches (January 2000-May 2015) were conducted for articles published in English, and limited to clinical trials using the key words ranibizumab, DR, DME, anti-VEGF, and DR treatment. Study Selection and Data Extraction: Following PubMed, Science Direct, Google Scholar, and ClinicalTrials.gov searches, 4 clinical trials were identified and included in this review. Phase III/IV studies evaluating the clinical efficacy of ranibizumab versus placebo, ranibizumab versus laser, and ranibizumab versus other anti-VEGF agents were selected and evaluated. Data Synthesis: Ranibizumab administered to patients with DME for 12 to 36 months improved and prevented worsening of visual acuity. At month 36 the ranibizumab-treated eyes had a >2 or >3 step DR improvement compared with the sham crossover eyes. Ranibizumab was also found to be superior to laser treatment. Patients receiving ranibizumab gained 6.0 letters, improved tritan and protan color contrast thresholds, and demonstrated improved retinal sensitivity versus the subjects receiving laser treatment who lost 0.9 letters. When ranibizumab was compared with other anti-VEGF agents (aflibercept, pegaptanib, and bevacizumab), it was not always demonstrated to be significantly superior. Conclusion: Ranibizumab has been shown to be safe and efficacious for use in the treatment of DR in patients with DME. Thus, it is an alternative treatment approach to laser photocoagulation therapy.