The breakthrough potential of aptamer therapeutics
Since their initial explosion onto the market, there is a growing pipeline demonstrating the promise of aptamer therapeutics across a range of indications.
The first aptamer therapeutic was approved by the FDA in 2004. From the discovery of aptamers in 1990, this was a rapid journey to the first therapeutic approval in just 14 years. Considering the average time for drug development, including all clinical trial phases, is 10-15 years, aptamers showed no delay in proving their therapeutic potential.
The dawn of aptamer therapeutics
When it was approved in 2004, Eyetech’s pegaptanib sodium injection (Macugen) was hailed as a revolutionary, breakthrough treatment for wet AMD, which robbed patients of their sight and had no other FDA-approved treatment. It was the first in what was then a new class of anti-vascular endothelial growth factor (VEGF) drugs and was said to represent a new era in treatment of wet AMD. It also was the first therapeutic drug delivered by intraocular injection. With peak net product revenue of $175-190 million in 2005, pegaptanib led the market for a number of years as an ophthalmologic treatment.
Aptamer therapeutics mature through the pipeline
Since pegaptanib, the emergence of further aptamer therapeutics has been slower, while researchers refined the technology and developed an increased understanding of how best to apply these molecules as therapeutics. But we are now beginning to see this modality making its way through the clinical pipeline to market.
|Aptamer Therapeutic||Disease indication||Phase 1||Phase 2||Phase 3||Approved|
|Neovascular wet (age-related) vascular degeneration|
|Geographic atrophy secondary to age-related macular degeneration|
|Autosomal recessive Stargardt disease|
|Aptoll||Acute ischaemic stroke|
Aptamers to multiple indications, from ophthalmology to oncology and infectious disease, are now in the clinic, with a second aptamer therapeutic, avacincaptad pegol, having successfully completed phase III trials.
Aptamer therapeutics tailored to therapeutic strategy
The flexibility of the aptamer format with both DNA aptamers and modified RNA aptamers available allows different therapeutic strategies to be embraced with aptamer therapeutics. Modified RNA aptamers incorporate inverted thymidine nucleotides to cap the 3’ end, fluorine and O-methyl modified nucleotides within the aptamer sequence, and the addition of a large polyethylene glycol (PEG) group to the aptamer. These modifications are used to extend the half-life of the aptamer therapeutic in vivo.
DNA aptamers, in contrast, typically offer shorter half-lives suitable for ‘hit-and-run’ strategies, where the aptamer therapeutic can quickly reach its target, induce an effect, and be excreted or degraded. In this case, the small size of the aptamer and accessibility of the DNA structure to endogenous enzymes facilitate the short half-life.
Of the current aptamer therapeutics under clinical trial, five are composed of RNA, two of DNA and one (AON-D21) is a mixed aptamers containing nucleotides of both DNA and RNA.
A further integration to support aptamer stability in vivo is the use of enantiomers, which are harder for endogenous enzymes to degrade. Three of the current aptamer therapeutics have utilised this approach, NOXA12, NOXE36 and AON-D12, using L-RNA nucleotides to synthesise the aptamer therapeutic for a longer half life.
As more aptamer therapeutics progress through the clinical pipeline there is increasing evidence of the potential of this therapeutic format, with more lessons learned as we go. At the same time manufacturers are now focused on improving CMC processes for these molecules to support the developers of this new modality, with reduced costs while maintaining the excellent product consistency that has long been associated with aptamers. To find out more about the cost and time to clinic of aptamers download our white paper or get in touch with our experts.