Personalized medicine – Benefits and drawbacks

A core advantage of personalized medicine is that it enhances efficacy and safety of therapies. For instance, a clinical pharmacogenetics assay may distinguish patients’ response to drug or their response to adverse effects of the drug (Spear, Heath-Chiozzi & Huff, 2001, p. 201). By distinguishing the responses to the drug, the assay would help in determining the efficacy of the drug in different populations thus aiding in administering the most effective alternative to a given population. Additionally, such a pharmacogenetics assay, by distinguishing the susceptibility of different subpopulations to adverse effects, would provide the safety profile of a particular drug thus avoiding the administration a drug with substantial adverse effects to a vulnerable population (Spear, Heath-Chiozzi & Huff, 2001).

Some benefits derived from use of personalized medicine are evident in cancer therapy. For instance, Herceptin, used in breast cancer therapy has shown efficacy in HER2-positive breast cancers, a more aggressive type of breast cancer that is less responsive to treatment compared to other breast cancers (Bates, 2010). In such HER2-positive cancers, the variations in genes induce the overexpression of human epidermal growth factor receptor 2 (HER2), thus facilitating growth of cancerous cells (Bates, 2010). By testing breast-cancer patients for HER2 over-expression, patients exhibiting overexpression would receive HER2-targeted medication (e.g. Herceptin) thus reducing the risk of recurrence of breast cancer (Bates, 2010). Accordingly, genetic testing in this respect helps to classify the breast cancers into subgroups, which facilitate the administration of effective therapies. Another personalized medication in cancer therapy is Gleevec, which is effective in chronic myeloid leukemia (Bates, 2010).

Away from cancer treatment, another benefit of personalized medicine is evident in sensitivity to warfarin, an anticoagulant used to prevent formation of blood clots in vessels. Warfarin therapy is complicated by wide variation in how patients respond to its administration thus complicating the process of determining the effective dose in a particular patient (Schwarz et al., 2008). Such variations are attributed to gene polymorphism in genes encoding CYP2C9 and VKORC1 (Schwarz et al., 2008). Patients with different genotypes of CYP2C9 and VKORC1 exhibit different sensitivities to warfarin administration (Schwarz et al., 2008). By defining the patients’ gene profiles, gene testing would help in determination of effective doses for different patients thus avoiding toxicity or administration of an ineffective dose.

Although development of personalized medicine through gene technology offers potential for better treatments, various challenges limit realization of such potential. Firstly, multiple genes could contribute to a drug-related response thus identification of a sole biomarker for a particular drug may not correspond to a positive predictive value for such a genomic biomarker (Spear, Heath-Chiozzi & Huff, 2001). When this is the case, use of such a biomarker to inform on drug choices could result into negative outcomes where the other (unmarked) genes exhibit their influence. Even when polymorphism in a particular gene is identified as the source of variations in patients’ drug responses, the possibility of multiple alleles of such a gene complicates the establishment of effective personalized therapies (Spear, Heath-Chiozzi & Huff, 2001; Saade, 2011). Other limitations to developing personalized medicine using genomic markers include meeting the costs for clinical trials and low numbers of individuals exhibiting the genetic variance of interest, which could prevent identification of clinically relevant subgroups (Spear, Heath-Chiozzi & Huff, 2001). proceed to the conclusion.

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