Ranibizumab

Ranibizumab (trade name Lucentis) is a monoclonal antibody fragment (Fab) derived from the same parent mouse antibody as bevacizumab (Avastin). It is much smaller than the parent molecule and has been affinity matured to provide stronger binding to VEGF-A. It is an anti-angiogenic that has been approved to treat the "wet" type of age-related macular degeneration (ARMD), a common form of age-related vision loss.

Some investigators believe that bevacizumab at an average cost of $42 a dose (in the U.S.) is as effective as ranibizumab at an average cost of $1,593 a dose.^[2][3]

Ranibizumab was developed by Genentech and is marketed in the United States by Genentech and elsewhere by Novartis,^[4] under the brand name Lucentis.

Mechanism of action

Ranibizumab binds to and inhibits a number of subtypes of vascular endothelial growth factor A (VEGF-A).^[5] VEGF may trigger the growth of new vessels, which may leak blood and fluid into the eye. These leaky blood vessels may contribute to macular edema and choroidal neovascularization, resulting in the wet type of ARMD.

By blocking VEGF-A in the eye, ranibizumab may prevent and reverse vision loss caused by wet macular degeneration.

Administration

The drug is injected intravitreally (into the vitreous humour of the eye) once a month. If monthly injections are not feasible, the regimen may be reduced to 1 injection every 3 months after the first 4 months.

However, dosing every 3 months is linked to a loss of approximately 5 letters (1 line) in visual acuity for the following 9 months as compared with dosing on a monthly basis. Large phase 3 clinical trials (MARINA and ANCHOR) which randomized patients with wet macular degeneration showed that 95% of ranibizumab-treated patients maintained visual acuity compared with 62% of those administered placebo (P < .01) at 1 year; moreover, up to 40% demonstrated an improvement in vision of at least 3 lines. Vision maintenance and loss were defined as a loss of less than 15 letters and a gain of 15 or more letters in visual acuity, respectively, as measured using the Early Treatment of Diabetic Retinopathy eye chart.

Side effects

The most common side effects in clinical trials were conjunctival hemorrhage, eye pain, vitreous floaters, increased intraocular pressure, and intraocular inflammation.

Although there is a theoretical risk for arterial thromboembolic events in patients receiving VEGF-inhibitors by intravitreal injection, the observed incidence rate was low (< 4%) and similar to that seen in patients randomized to placebo.

Serious adverse events related to the injection procedure occurred with an incidence rate of less than 1% and included endophthalmitis, retinal detachment, and traumatic cataracts. Other serious ocular adverse events observed among ranibizumab-treated patients (incidence rate < 1%) included intraocular inflammation and blindness.^[5]

Marketing

On November 3, 2010, The New York Times reported that Genentech began offering secret rebates to about 300 ophthalmologists in an apparent inducement to get them to use more ranibizumab rather than their less expensive bevacizumab, in anticipation of the result of a comparative study trial [1] – sponsored by the National Eye Institute – of ranibizumab and bevacizumab to assess the relative safety and effectiveness in treating ARMD. Some retina specialists consider the tactic bribery. In 2008, bevacizumab cost Medicare only $20 million for about 480,000 injections, while ranibizumab cost Medicare $537 million for only 337,000 injections.^[6] A small study showed no superior effect of ranibizumab versus bevacizumab in direct comparison.^[7] A large clinical trial was published in the New England Journal of Medicine and showed no superior effect of ranibizumab. No difference in side effects could be found.^[8]

References

External links

• Official website Genentech