Discovery Of Biologics Answers | Assessment Answer

Biologics are considered as large revolutionary molecules. These molecules are capable of modifying the biological responses of the body. These biologics are the result of target-based drug discovery where the biologists used their complete knowledge of the disease pathophysiology to recognize the main ‘culprit’ biological targets and against those culprits they managed to develop ‘biologics’ using advance manufacturing techniques (Singh et al. 2012). These biologics are helpful to inhibit the action of several components in the immune system, which play key roles in inflammation and considered as the main feature of Rheumatoid Arthritis (RA) (Nam et al. 2010). In the context of drug discovery process, the validation and the identification of TNF as a prospective therapeutic target lead to the expansion of biologics (infliximab) is discussed in following paragraphs.  

Target Identification and Validation

It is observed that enhanced expression of HLA-DR and presence of rheumatoid factors found in diseased joint synovium points to the immune pathogenesis of rheumatoid factors. Generally, IL-1 is followed by the mediators of the systematic inflammation such as CSF-2 (colony stimulating factor-2), TNF-α, IL-6 and others like CD-20 and IL-12 are also found synovium and identified as popular targets of biologics (Galloway et al. 2011).

Anti CD⁴⁺ was used in the first trials. However, the research was failed. After the collapse of CD⁴⁺ antibodies, the research was continued to recognize the main culprit, which could be blocked to inhibit the other factors of inflammation. In many types of research it is observed that use of rheumatoid synovial cell cultures showed that the mRNA expression for IL-1 is astonishingly extended in the synovial cell cultures while comparing with the expression of IL-1, which is derived from stimulated leucocytes (normal) (McInnes and Schett, 2011). The findings in this context are extremely helpful to prepare a model, which is may be used successfully outside the normal biological context to study the functional gene product, which involves Rheumatoid Arthritis (Drutskaya et al. 2010). Using the model, it is further found that antisera against TNF (Tumor Necrosis Factor) can oppose the expression of IL-1, within three days of administration (Aaltonen et al. 2012).  This finding further unraveled the new generation of an investigation, which consider TNF has the prime importance to coordinate the cytokine response in rheumatoid arthritis. Also, the effect of anti-TNF antisera on IL-8, IL-6 and GM-CSF was investigated. From the studies, it was established that recruitment of blood leucocytes due to the TNF through chemokines and adhesion molecules mediate the process of inflammation (Furst, 2010).

Testing of Biologics in animal models of Rheumatic Arthritis

In further researches, it is observed that the appearance of TNF (Tumor Necrosis Factor) and its receptor are facilitated in affected tissues (Galloway et al. 2011). ‘Hamster monoclonal antibodies” against TNF were tested in CIA (collagen induced arthritis) model of rheumatoid arthritis (considered as the best model). This test was helpful to prove the validity of TNF as the major target (biological factor) in rheumatoid arthritis. It is found that application of 300 and 500 µg weekly (twice) can minimize the intensity of the clinical symptoms (Aaltonen et al. 2012). As a result, the expression of TNF (precisely spatial expression) is reduced, and histologic symptoms of treated mice showed progress, which includes, cellular infiltrate reduction, chondrocyte apoptosis and joint destruction (Dixon et al. 2010). It is observed that dispensing of “anti human anti TNF-α monoclonal antibody" can stop the symptoms of spontaneous arthritis in "transgenic mice," which showed the over expression of TNF (Furst, 2010). It is also found that many researchers obtained promising results by using CIA model (Galloway et al. 2011).

Therapeutic agents with anti-TNF potential

Many researchers tried to find out biologics, which have miraculous therapeutic potentiality. To share the dream, many pharmaceutical industries tried to prepare different innovative agents. One of the fruitful results of these researches is he design of cA2, which is widely known as infliximab. Centocor first prepared this chimeric antibody against biological target TNF. The murine hybridoma was used to chimarized murine “Fv segment” with the human IgG1, K backbone (considered as Fc fragment).

Clinical studies

It is important to calculate the tolerable dose; therefore, to calculate the maximum tolerable dose, toxicity studies took place. From the previous studies, it was observed that 20mg/kg/2 weeks dose was enough to get the best result (Nam et al. 2010). However, also, different biomarkers such as ESR (erythrocyte sedimentation rate), IL-6 and (CRP) C-reactive protein are declining within seven days as well as the level of rheumatoid factors, resulting in the improvement of the clinical and symptomatic features (Dixon et al. 2010). 

On the other hand, in a "double-blind, randomized trial" placebo was compared with 1 and 10 mg/kg doses of cA2. After four weeks (washout periods), the experimental group and subjects of controls were infused with solutions, however, the appearance of which remained same. The response was further measured after 4^th week with the help of Harold Paulus criteria, where most of the respondents were found in 10mg/kg doses.

After the first trial efficacy and safety proof were established and then phase 2 trials were introduced. In phase 2 trials, 1, 3 and 10 mg/kg of cA2 was administered with or without 7.5 mg of methotrexate/week. From the result, it was observed that all doses have the synergic response with MTX while comparing with mono-therapy. 

After the completion of phase 2 trials, phase 3 trial began. This phase 3 trial was also known as ATTRACT (Anti-Tumor Necrosis Factor Trial in Rheumatoid Arthritis with Concomitant Therapy) trial and include the administration of MTX and infliximab.  Four doses (3 and 10 mg/kg for four weeks and eight weeks) of infliximab were compared with ‘MTX plus placebo’. In observation (at 30^th, 54^th and 102^nd week) showed that nearly 50% of patients have improved clinical symptoms as well as developed physical functions (Dixon et al. 2010).

On the other hand, the Taylor’s radiography demonstrated a single dose of infliximab could reduce 50% of granulocyte accumulation in joints. The license of using infliximab against TNF was permitted after showing the clinical trials. However, measurement of benefit to harm ratio of biologics are still under investigation.

References

Aaltonen, K.J., Virkki, L.M., Malmivaara, A., Konttinen, Y.T., Nordstrom, D.C. and Blom, M., 2012. Systematic review and meta-analysis of the efficacy and safety of existing TNF blocking agents in the treatment of rheumatoid arthritis. PLoS One, 7(1), p.e30275.

Dixon, W.G., Hyrich, K.L., Watson, K.D., Lunt, M., Galloway, J., Ustianowski, A., Symmons, D.P.M. and BSRBR Control Centre Consortium, 2010. The drug-specific risk of tuberculosis in patients with rheumatoid arthritis treated with anti-TNF therapy: results from the British Society for Rheumatology Biologics Register (BSRBR). Annals of the rheumatic diseases, 69(3), pp.522-528.

Drutskaya, M.S., Efimov, G.A., Kruglov, A.A., Kuprash, D.V. and Nedospasov, S.A., 2010. Tumor necrosis factor, lymphotoxin, and cancer.IUBMB life, 62(4), pp.283-289.

Furst, D.E., 2010, April. The risk of infections with biologic therapies for rheumatoid arthritis. In Seminars in arthritis and rheumatism (Vol. 39, No. 5, pp. 327-346). WB Saunders.

Galloway, J.B., Hyrich, K.L., Mercer, L.K., Dixon, W.G., Fu, B., Ustianowski, A.P., Watson, K.D., Lunt, M., Symmons, D.P. and BSRBR Control Centre Consortium, 2011. Anti-TNF therapy is associated with an increased risk of serious infections in patients with rheumatoid arthritis especially in the first six months of treatment: updated results from the British Society for Rheumatology Biologics Register with special emphasis on risks in the elderly. Rheumatology, 50(1), pp.124-131.

Galloway, J.B., Hyrich, K.L., Mercer, L.K., Dixon, W.G., Ustianowski, A.P., Helbert, M., Watson, K.D., Lunt, M. and Symmons, D.P.M., 2011. The risk of septic arthritis in patients with rheumatoid arthritis and the effect of anti-TNF therapy: results from the British Society for Rheumatology Biologics Register. Annals of the rheumatic diseases, p.annrheumdis152769.

McInnes, I.B., and Schett, G., 2011. The pathogenesis of rheumatoid arthritis. New England Journal of Medicine, 365(23), pp.2205-2219.

Nam, J.L., Winthrop, K.L., Van Vollenhoven, R.F., Pavelka, K., Valesini, G., Hensor, E.M.A., Worthy, G., Landewé, R., Smolen, J.S., Emery, P. and Buch, M.H., 2010. Current evidence for the management of rheumatoid arthritis with biological disease-modifying antirheumatic drugs: a systematic literature review informing the EULAR recommendations for the management of RA. Annals of the rheumatic diseases, p.annrheumdis126573.

Singh, J.A., Furst, D.E., Bharat, A., Curtis, J.R., Kavanaugh, A.F., Kremer, J.M., Moreland, L.W., O'Dell, J., Winthrop, K.L., Beukelman, T. and Bridges, S.L., 2012. 2012 Update of 2008 American College of Rheumatology recommendations for the use of disease‐modifying antirheumatic drugs and biologic agents in the treatment of rheumatoid arthritis. Arthritis care & research, 64(5), pp.625-639.