The whole area of oligonucleotides-based drug is getting a much higher "business" activities since the approval of Isis' Vitravene. As this is still a relatively new area, the quantitation of oligonucleotides-based drugs in any biological matrices is not as established as small organics or proteins and vaccines.

QPS used both chromatographic and ligand-binding methods for quantitation. For chromatographic methods, we have used the "traditional" LC/MS/MS as well as LC/UV assays to look at plasma exposure. The choice of detection and quantitation whether to use MS/MS or UV is based on the primary structure, the number of monomeric units, and the desired study design. We have developed and validated both LC/MS/MS and LC/UV assays for oligonucleotides-based drug.

Examples are:
1. The "standard" oligonucleotides and anti-sense oligonucleotides drugs using hybridization-ELISA method
2. An oligonucleotides drug of around 4,500 Da using LC/MS/MS. As this was the first documented LC/MS/MS human plasma method for an oligonucleotide to be submitted to FDA, the sponsor was insistent of using a 6-day validation parameter rather than the 3-days recommended by the Bioanalytical Method Guidance document.
3. A PEGylated oligonucleotides-based drug of around 35,000 Da using LC/UV.

The main advantage of the hybridization-ELISA method is the sensitivity, which can be in the low or sub-ng/mL range. Although the LLOQ of the chromatographic methods is usually in the ng/mL range, this may be adequate depending on the target matrix and the study design. The main advantage of chromatographic method is the ability to separate, detect, and quantitate the parent drug from the exo/endo-nucleoases degraded metabolites.