Ans. d. Dose independent pharmacokinetics (Ref: Harrison 19/e p2147,18/e p2749; Katzung 12/e p646; htt[://www.isdbweb. org/documents/file/1442_2pdf)Pharmacokinetics of rituximab (monoclonal antibodies) is dose dependent.'The rate of uptake and elimination of antibodies by target-mediated pathways is a function of dose and the expression level of the target, as well as a function of the kinetics of receptor internalization and intracellular catabolism http:// www.isdbweb.org/documents/file/1442_2.pdfRituximabRituximab is a murine-human monoclonal IgG1 (human Fc) that binds to the CD20 molecule on normal and malignant B lymphocytesQMechanism of Action:The mechanism of action includes complement-mediated lysis, antibody-dependent cellular cytotoxicity, and induction of apoptosis in the malignant lymphoma cellsQ.Indications:Approved for relapsed or refractory low-grade or follicular B cell non-Hodgkin's lymphomaQ.Approved for the treatment of refractory RA in combination with methotrexate and has been shown to be more effective for patients with seropositive than seronegative diseaseQ.Side-effects:Associated with mild-to- moderate infusion reactions as well as an increased risk of infectionQ.Notably, there have been isolated reports of a potentially lethal brain disorder, progressive multifocal leukoencephalopathy (PML), in association with rituximab therapy.It has been also shown to cause Tuberculosis.Pharmacokinetics:The rate of uptake and elimination of antibodies by target-mediated pathways is a function of dose and the expression level of the target, as well as a function of the kinetics of receptor internalization and intracellular catabolism.Monoclonal antibodies marketed for therapeutic useAntibodyIsotype/structurePrimary indicationAbciximabChimeric mouse/human FabPrevention of cardiac ischemic complicationsAdalimumabHuman lgG1Rheumatoid arthritisAlemtuzumabCDR-grafted rat/human IgG1B-cell chronic lymphocytic leukemiaBasiliximabChimeric mouse/human IgG1Prophylaxis of acute organ rejectionBevacizumabCDR-grafted mouse/human lgG1Colorectal, lung, and breast cancerCertolizumab pegotPEGylated FabCrohn's diseaseCetuximabChimeric mouse/human lgG1Head and neck cancer, colorectal cancerDaclizumabCDR-grafted mouse/human lgG1Prophylaxis of acute organ rejectionEculizumabCDR-grafted mouse/human lgG2/lgG4Paroxysmal nocturnal hemoglobinuriaEfalizumabCDR-grafted mouse/human lgG1PsoriasisGemtuzumab ozogamicinCDR-grafted mouse/human lgG4Acute myeloid leukemiaIbritumomab tiuxetanMurine lgG1Non-Hodgkin's lymphomaInfliximabChimeric mouse/human lgG1Rheumatoid arthritis, Crohn's diseaseMuromonab-CD3Murine lgG2aAcute organ rejectionNatalizumabCDR-grafted mouse/human lgG4Multiple sclerosisOmalizumabCDR-grafted mouse/human lgG1AsthmaPativizumabCDR-grafted mouse/human lgG1Prevention of respiratory tract diseasePanitumumabHuman lgG2Colorectal cancerRanibizumabCDR-grafted human IgG1 FabMacular degenerationRituximabChimeric mouse/human IgG1Non-Hodgkin's lymphoma, rheumatoid arthritisTositumomabMurine lgG2aNon-Hodgkin's lymphomaTrastuzumabCDR-grafted mouse/human lgG1Breast cancerCDR, complementarity determining region: IgG, immunoglobulin G.