by Dan Roberts
A substance in the body called Vascular Endothelial Growth Factor (VEGF) is responsible for the growth of new blood vessels. It promotes this growth by stimulating the endothelial cells, which form the walls of the vessels and transport nutrients and oxygen to the tissues. Evidence shows that when the retinal pigment epithelial (RPE) cells begin to wither from lack of nutrition (a condition called “ischemia”), the VEGF goes into action to create new vessels. This process is called “neovascularization,” and it acts as a restorative function in other parts of the body. In the retina, however, the vessels do not form properly, and leaking results. This leakage causes scarring in the macula and eventual loss of central vision.
Antiangiogenic drugs prevent the VEGF from binding with the receptors on the surface of the endothelial cells. In most cases, the drugs are injected into the vitreous of the eyeball, then pass into the subretinal space, where the vessels proliferate. Neovascularization is then blocked, preventing bleeding into the retina. New research is looking for less invasive and burdensome introduction of the drugs by way of topical eye drops, implanted timed release capsules, and implanted ports of delivery.
This is information on current anti-angiogenic drugs being studied or already approved for wet AMD:
Macugen (pegaptanib sodium) [approved 2004]
Lucentis (ranibizumab) [approved 2006]
EYLEA (aflibercept) [approved 2011]
Avastin (bevacizumab) [available off-label since 2007]
Pazopanib [updated 11/17]
Squalamine (OHR-102) [updated 2/17]
PAN-90806 [updated 11/17]
OPT-302 [updated 11/17]
ICON-1 [updated 11/17]
RGX-314 [updated 11/17]
RTH258 (brolucizumab) [updated 11/17]
Macugen (pegaptanib sodium)
Macugen, made by OSI EyeTech Pharmaceuticals, was the first antiangiogenic drug to gain FDA approval. Pegaptanib is a chemically synthesized strand of genetic material that bonds with VEGF cells to block replication. A large trial of Macugen on 1,196 patients at 117 centers around the world was completed in 2003. In November of that year, data presented to the American Academy of Ophthalmology (AAO) showed that Macugen stabilized or improved vision in 33% of the patients in the trials, while the same results occurred in 23% of a control group not given Macugen. As many as 71% of the patients given Macugen lost less than three lines of vision during the year, compared with 55% in the control group. The drug is injected directly into the eye every six weeks, or about nine times a year.
Working in conjunction with Pfizer Ophthalmics, Macugen gained FDA approval on December 17, 2004, and was ready for public use beginning in 2005.
On October 11, 2007, a retrospective study showed that results from Macugen treatment may be better than originally announced. The study, published in the September 2007 issue of Retina, found that overall, 90% of patients had responded to pegaptanib treatment at 9.1 months mean follow-up. Specifically, 18 patients (20%) gained three or more lines of vision, and vision stabilized in 63 patients (70%), which the authors defined as the prevention of a loss of three lines of vision.
Macugen is also being studied for expanded use in patients with diabetic macular edema and central retinal vein occlusion.
Genentech, Inc. announced on May 23, 2005 that a Phase III clinical study of the investigational drug Lucentis (ranibizumab) met its primary efficacy endpoint of maintaining vision in patients with wet AMD. Approximately 95 percent of patients maintained or improved vision (defined as a loss of less than 15 letters in visual acuity) at one year when treated with Lucentis injections compared to approximately 62 percent of those treated in the control arm. Vision improvement was an unexpected result that had not been seen at a significant level in other antiangiogenic drug trials. Lucentis is approved for use in the European Union, Switzerland, India, Canada and the United States. A regulatory decision in Australia is expected before the end of 2007.
On January 14, 2006, one-year data from the second pivotal Phase III study of Lucentis were presented at the Macula 2006 meeting in New York. Data showed that, for the second time in a large, Phase III study, Lucentis improved vision in patients with wet AMD.
On November 13, 2006, several new findings were presented at the 2006 AAO meeting:
Elias Reichel, M.D. reported that in the MARINA trials, there was improvement at all visual acuity levels, but there was not a big difference if the patient’s baseline vision was either low or excellent. This “floor-to-ceiling” effect is not unusual with this kind of study, but it is useful information for patient communicating with patients about expectations.
Nancy Holekamp, M.D., discussed key anatomic endpoints in the MARINA trials, in particular, the total lesion area over time (no growth of the lesion area was noted in the treated patients), the mean area of leakage (the amount of decrease was statistically significant) and the mean foveal retinal thickness (treated eyes showed a significant thinning of the retina). The bottom line is that all anatomic outcomes from the trial favored Lucentis, and the treatment is so effective over a long period of time without any signs of toxicity, there is no indication that anything in lieu of Lucentis should be used to treat wet AMD.
Peter Kaiser, M.D., reported on subgroup analysis of Genentech’s PIER study. The primary endpoint was met, showing a difference of 16 letters visual acuity between the treated group and the sham group. Further, the dosing regimen was effective, but the visual acuity benefit was not as robust when injections went from monthly to quarterly. The persistence of monthly injections may depend upon who has dry lesions and who has wet lesions at the 5th month. The dry lesion group did better than the wet lesion group with quarterly dosing. This data is pointing toward better prediction of dosage outcomes for individual patients.
On February 15, 2007, Dr. Kaiser reported two-year results of the Phase 3 ANCHOR trial comparing Lucentis with photodynamic therapy (PDT) for wet AMD. The study showed that Lucentis helps maintain vision, with few adverse effects, significantly better than PDT. 89.9% of patient randomised to Lucentis in a head-to-head comparison with Visudyne for photodynamic therapy (PDT) lost fewer than 15 letters on a visual acuity chart at 24 months compared to 65.7% of those treated with PDT. 78% of the Lucentis-treated group maintained their baseline visual acuity or gained letters, compared to only 29% of the PDT group. Overall, patients randomised to Lucentis had a 20.5 letter benefit at 24 months (+10.7 EDTRS letters) compared to those treated with PDT (-9.8 letters). This was similar to visual acuity seen at 12 months (+11.3 letters with Lucentis vs -9.6 letters with PDT).
On February 23, 2008, the final results from Cohort 1 of the Phase IIIb SAILOR study of Lucentis in patients with wet AMD were presented on February 23, 2008 at the Bascom Palmer Eye Institute’s Angiogenesis meeting by Dr. David Boyer (Retina-Vitreous Associates Medical Group, Los Angeles). The final, one-year data support the long-term safety and efficacy profile of Lucentis.
The study, titled “Ranibizumab (Lucentis) Safety in Previously Treated and Newly Diagnosed Patients with Neovascular Age-related Macular Degeneration (AMD): The SAILOR Study,” was designed to evaluate the safety of two different doses of Lucentis (0.5 mg, the FDA-approved dose, and 0.3 mg) administered once a month for three months and thereafter as needed based on re-treatment criteria.
For more detail in all of these areas of study, see www.lucentis.com.
EYLEA (aflibercept injection, formerly VEGF Trap-Eye)
In August 2008, Regeneron Pharmaceuticals, Inc. and Bayer HealthCare AG announced that patients with wet AMD receiving EYLEA (aflibercept injection) in a Phase 2 extension study on an “as needed” dosing schedule continued to show highly significant improvements in retinal thickness and vision gain at 52 weeks. There were no drug-related serious adverse events, and treatment was generally well-tolerated.
For all dose cohorts combined, there was a 5.3 mean letter gain in visual acuity at the end of 52 weeks. The mean decrease in retinal thickness was 130 microns versus baseline. During weeks 12 to 52, patients from all dose groups combined received, on average, only two additional injections. This supported Regeneron’s expectation that, with EYLEA treatment, patients’ visual acuity would improve over time without the need for monthly intravitreal injections.
A phase 3 study, VIEW 1, began enrolling patients in late 2007. The VIEW 1 study compared EYLEA and Lucentis. A phase 2 study in diabetic macular edema (DME) was also completed. EYLEA injected into the eye every two months was found to be as effective as monthly doses of Lucentis, and monthly monitoring of patients receiving EYLEA was not necessary.
On June 17, 2011, the Food and Drug Administration advisory panel voted unanimously to recommend EYLEA as a treatment for wet AMD. The advisers also said the injected drug could be given once every two months. This was an improvement upon the typical 4-6 week dosings of both Lucentis and Avastin.
Finally, on November 18, 2011, Regeneron announced that the FDA had approved EYLEA for treatment of patients with wet AMD. Recommended dose is 2 mg every four weeks for the first 12 weeks, followed by 2 mg every eight weeks. EYLEA offers less frequent injections than either Lucentis (4 weeks) or Avastin (6 weeks), and there are no monitoring requirements.
Since September 2012, Eylea has also gained approval in the U.S., Europe, and Japan for use in treating wet AMD, diabetic macular edema, and neovascular myopic degeneration. For more information, see www.regeneron.com.
Avastin (bevacizumab), has been shown in preliminary off-label studies to stop blood vessel growth and leakage in the retinas of patients with macular degeneration. Testing began in March 2005 at the Bascom Palmer Eye Institute in Miami under the leadership of Dr. Philip Rosenfeld. In July 2005, Dr. Peter Campochiaro followed with subjects at the Johns Hopkins Medical Center in Baltimore. Potential side effects, according to Rosenfeld, are increased risk of stroke or heart attack in patients taking chemotherapy, and elevation of blood pressure. Systemic infusions of Avastin, he said would be needed every few months.
On February 15, 2007, Elias Reichel, M.D. reported to Hawaiian Eye/Retina 2007 that Avastin has shown good results in a small retrospective case series for treatment of neovascularization from myopic degeneration. 15 eyes studied showed a mean improvement in acuity of 3 lines, central foveal thickness decreased an average of 93 micrometers and no complications.
In May 2011, first year results of the Comparison of AMD Treatments Trial (CATT) were announced. The report focused on the relative safety and efficacy of Lucentis and Avastin. After one year, the two compounds have been found to be extremely similar in their improvement of mean visual acuity and the occurrence of adverse events. Five related trials were also undertaken in the UK and Europe.
At the end of the 2-year comparison study, The National Institutes of Health reported that both drugs improved vision when administered monthly or on an as needed basis. Patients receiving Lucentis, however, fully maintained first-year vision gains with an average 5.7 injections in the second year. In contrast, patients treated with Avastin experienced a greater decline in vision despite receiving significantly more injections over the two year period. In addition, secondary anatomical outcomes were significantly better with Lucentis. For more information, see www.nih.gov/news/health/apr2012/nei-30a.htm
Researchers from GlaxoSmithKline state that topical administration of pazopanib causes regression of already established CNV in patients with neovascular AMD. A 28 day safety study in February 2010 revealed no serious adverse events in the eye related to the drug. However, some mild to moderate symptoms were reported in some patients. A phase 2 trial has also been completed. More information.
Squalamine (Ohr Pharmaceutical) is an anti-angiogenic small molecule that counteracts not only Vascular Endothelial Growth Factor (“VEGF”) but also other angiogenic growth factors such as Platelet Derived Growth Factor (“PDGF”) with high potency at nanomolar concentrations. Recent clinical evidence has shown PDGF to be an additional key target for the treatment of wet-AMD.
Using the intravenous formulation in over 250 patients in Phase 1 and Phase 2 trials for the treatment of wet-AMD, Squalamine demonstrated favorable biologic effect and maintained and improved visual acuity outcomes, with both early and advanced lesions responding. Ohr Pharmaceuticals has developed an eye drop formulation of Squalamine for the treatment of wet AMD designed for self-administration. Preclinical testing demonstrated that the eye drop formulation is both safe to ocular tissues and achieves in excess of target anti-angiogenic concentrations in the tissues of the back of the eye.
In May 2012, the Squalamine eye drop program was granted Fast Track Designation by the FDA, and the drug entered Phase 3 trials. Unfortunately, Ohr Pharmaceuticals had to temporarily suspend the study in February 2017 and stop further recruitment. Current subjects will still, however, continue to receive the treatment, since safety issues were not the reason for the suspension.
PAN-90806 is a topical eye drop for the treatment of neovascular AMD, diabetic retinopathy, and potentially diabetic macular edema (DME). It is being developed by Panoptica and began a phase 1 clinical trials in early 2014, a 2-month open-label study of approximately 30 patients at 15 to 20 sites in the U.S. The study was completed in May 2016. More information.
OPT-302 is soluble receptor developed by Opthea Pty Ltd. It is a derivative of VGX-300 which has been optimised for local ocular administration. OPT-302 potently and specifically blocks VEGF-C and VEGF-D from binding and activating VEGFR-2 and VEGFR-3. Opthea is recruiting for Phase 2A clinical trials.
The EMERGE study examined the hypothesis that a protein called Tissue Factor (TF), when out of control, initiates inflammation and angiogenesis, resulting in wet AMD. ICON-1 is thought to block the protein and reverse the progression of the disease, both alone and in combination with Lucentis.
Phase 2a results showed that ICON-1 was well tolerated and that in combination with anti-VEGF therapy treated both the symptoms and the underlying process driving inflammation and CNV. The combination effectively reduced CNV lesion size, increased the durability of effect and improved removal of pathologic fluid from the retina.
Based on these positive results, the company plans to initiate a Phase 2b study of ICON-1 in combination with anti-VEGF treatment in 2018. This trial will be larger than the Phase 2a study and will explore a higher dose of ICON-1 for a longer period of time. For more information see http://iconictherapeutics.com/pipeline/icon-1/
RGX-314 differs from current therapeutics in that it includes a gene vector (NAV AAV8) which encodes an antibody fragment designed to neutralize VEGF (vascular endothelial growth factor) activity. This modifies the pathway for formation of new leaky blood vessels which lead to retinal fluid accumulation and vision loss.
Six leading retinal surgery centers across the United States are expected to participate in the Phase I trial of RGX-314. For further details on the trial, enrollment criteria and eligibility, contact firstname.lastname@example.org or visit https://clinicaltrials.gov/ct2/show/NCT03066258.
The purpose of this study by Novartis is to compare RTH258 ophthalmic solution for intravitreal (IVT) injection at two dosage levels to aflibercept solution for IVT injection (2 mg) in subjects with untreated active choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) in the study eye. Phase 3 of this study is ongoing with an estimated completion date of May 2018.For more information, see https://www.novartis.com/news/media-releases/novartis-brolucizumab-rth258-demonstrates-superiority-versus-aflibercept-key