The pharmacokinetics of rituximab following an intravitreal injection

Prolongation of activity of single intravitreal bevacizumab by adjuvant topical aqueous depressant (Timolol-Dorzolamide)

BACKGROUND

To evaluate the efficacy of timolol-dorzolamide drops used to decrease aqueous outflow from the eye on the prolongation of the biological activity of intravitreal bevacizumab.

METHODS

Thirty-eight eyes of 38 patients with macular edema (ME) following retinal vein obstruction (RVO) were enrolled. These patients were randomly assigned into 2 groups: timolol-dorzolamide drops twice daily (n = 19) or no eyedrops (control; n = 19). All patients received 1.25 mg (in 0.05 mL) of bevacizumab intravitreally and were examined before treatment, 1 week after injection, and then every 4 weeks after injection. For each patient, visual acuity (VA), intraocular pressure (IOP), and central retinal thickness (CRT) by optical coherence tomography (OCT) were recorded before injection and at each visit after injection. The mean CRT at each timepoint was considered to directly reflect the biological activities of bevacizumab at those times.

RESULTS

The mean CRT measured by OCT showed a significant decrease 1 week after treatment in both groups, and this difference was maintained for a total of 9 weeks (paired t-test, <0.001). The mean CRT at 1 week post-injection showed no significant between-group difference (p = 0.781). At 5 weeks post-injection, the timolol-dorzolamide group showed a significantly smaller mean CRT than the control group (p = 0.032). The difference in mean CRT between the 2 groups disappeared, however, at 9 weeks post-injection (p = 0.462). In both groups, VA improved significantly 1 week after injection, and these changes were maintained to 9 weeks post-injection in both groups. The mean VA of the 2 groups showed no difference at any time.

CONCLUSIONS

Timolol-dorzolamide aqueous depressant drops may delay the elimination of intravitreal bevacizumab but clinical efficacy of the eyedrops have not been proven in this study.

Predicted biologic activity of intravitreal bevacizumab

PURPOSE

To create a time- and dose-dependent mathematical model that compares the intravitreal vascular endothelial growth factor (VEGF) binding activity of bevacizumab with that of ranibizumab.

METHODS

Intravitreal half-lives and relative equimolar VEGF binding activities of bevacizumab and ranibizumab were incorporated into a first-order decay model. Time-dependent bevacizumab activities (relative to ranibizumab) for different initial doses (1.25 and 2.5 mg) and reinjection intervals (single, weekly, and every 3 days) were calculated and graphed.

RESULTS

Twenty-seven days to 38 days after a single bevacizumab (1.25 mg) injection, the intravitreal VEGF binding activity would be comparable with that of ranibizumab at 30 days. Bevacizumab (2.5 mg) injections would need to be performed every 3 days for 1 month to equal the peak activity after a ranibizumab injection.

DISCUSSION

On the basis of this mathematical model, intravitreal bevacizumab maintains significant VEGF binding activity for 4 weeks to 5 weeks. More frequent bevacizumab injections increase the average binding activity but not to that seen with a single ranibizumab injection.

Intraperitoneal application of rituximab in refractory mantle cell lymphoma with massive ascites resulting in local and systemic response

In the past decade, rituximab in combination with polychemotherapy has become the standard approach in most patients with advanced CD20-positive B-cell lymphoma. In mantle cell lymphoma (MCL), follicular lymphoma and diffuse large B-cell lymphoma, rituximab has been used as monotherapy and in combination with various chemotherapy regimens in different treatment situations. Routinely, rituximab is given intravenously, but other routes of administration have also been described. Here, we report a 64-yr-old woman who was previously treated with three different chemotherapy regimens for stage IV MCL. No sustained clinical and radiological response could be achieved. The patient's general status declined and she developed massive ascites as the dominant clinical problem. Local, intraperitoneal administration of rituximab was initiated as an experimental treatment approach. After 11 doses of rituximab, the general status of the patient improved significantly, ascites resolved completely and computed tomography (CT) scans demonstrated a partial remission of intra-abdominal lymph nodes and splenomegaly. Furthermore, we observed a regression of mediastinal lymph nodes, pleural effusion and centrocytes in peripheral blood as well as improvement of anaemia. The response to the experimental treatment has maintained for more than 6 months. In summary, we observed a sustained local and systemic response to intraperitoneal administration of rituximab in a patient with heavily pretreated advanced MCL.

Novel approaches to retinal drug delivery

Research into treatment modalities affecting vision is rapidly progressing due to the high incidence of diseases such as diabetic macular edema, proliferative vitreoretinopathy, wet and dry age-related macular degeneration and cytomegalovirus retinitis. The unique anatomy and physiology of eye offers many challenges to developing effective retinal drug delivery systems. Historically, drugs have been administered to the eye as liquid drops instilled in the cul-de-sac. However retinal drug delivery is a challenging area. The transport of molecules between the vitreous/retina and systemic circulation is restricted by the blood-retinal barrier, which is made up of retinal pigment epithelium and endothelial cells of the retinal blood vessels. An increase in the understanding of drug absorption mechanisms into the retina from local and systemic administration has led to the development of various drug delivery systems, such as biodegradable and non-biodegradable implants, microspheres, nanoparticles and liposomes, gels and transporter-targeted prodrugs. Such diversity in approaches is an indication that there is still a need for an optimized noninvasive or minimally invasive drug delivery system to the eye. A number of large molecular weight compounds (i.e., oligonucleotides, RNA aptamers, peptides and monoclonal antibodies) have been and continue to be introduced as new therapeutic entities. However, for high molecular weight polar compounds the mechanism of epithelial transport is primarily through the tight junctions in the retinal pigment epithelium, as these agents undergo limited transcellular diffusion. Delivery and administration of these new drugs in a safe and effective manner is still a major challenge facing pharmaceutical scientists. In this review article, the authors discuss various drug delivery strategies, devices and challenges associated with drug delivery to the retina.

Intraocular use of rituximab

PURPOSE

To evaluate the toxicity of 1 mg of intraocular rituximab and to present a small case-series of patients treated with intravitreal rituximab.

METHODS

Rituximab (1 mg/0.1 ml) was injected in the vitreous of one eye of three Dutch-belted rabbits. Two animals were injected with balanced salt solution as controls. At 1 month the rabbits were killed and the eyes examined by light microscopy. Three patients (five eyes) with intraocular lymphoma were also treated with a 1 mg injection of rituximab.

RESULTS

The treated rabbit eyes and the control eyes showed no light microscopic evidence of ocular toxicity at 1 month following injection. The five human eyes of three patients have shown no evidence of intraocular toxicity with a median follow-up time of 3.6 months (range 2.0-6.4 months). One patient received a total of four injections in the right eye and three injections in the left eye.

CONCLUSION

Intravitreal rituximab at a dose of 1 mg does not appear to cause toxicity in rabbit eyes and in the five eyes of three patients.