title: An approach for conjugation of (177) Lu- DOTA-SCN- Rituximab (BioSim) & its evaluation for radioimmunotherapy of relapsed & refractory B-cell non Hodgkins lymphoma patients.
abstract: OBJECTIVE
  The prerequisite of radioimmunotherapy is stable binding of a radionuclide to monoclonal antibodies, which are specific to the tumour-associated antigen. Most B-cell lymphomas express CD20 antigen on the surface of the tumour cells, making it a suitable target for therapeutic radioactive monoclonal antibodies. In the present study, the immunoconjugate of biosimilar Rituximab (Reditux™) and macrocyclic chelator, p-SCN-Bz-DOTA, was prepared and radiolabelled with Lutetium-177 followed by quality control procedures.
  
  
  METHODS
  Rituximab(BioSim) was desalted with sodium bicarbonate (0.1M, pH 9.0) and incubated with DOTA-SCN (1:50). The effectiveness of the conjugation was evaluated by determining the number of chelators per antibody molecule. This conjugate was radiolabelled with Lutetium-177 and purified using PD10 column. The quality control parameters like pH, clarity, radiochemical purity, in vitro stability and sterility were studied. Immunoreactivity of 177 Lu-DOTA-Rituximab (BioSim) was assessed using RAMOS cells. The radioimmunoconjugate (RIC) after stringent quality assurance was injected in three patients and the biodistribution profile was analysed.
  
  
  RESULTS
  An average of 4.25 ± 1.04 p-SCN-Bz-DOTA molecules could be randomly conjugated to a single molecule of Rituximab (BioSim).The radiochemical purity of the labelled antibody was > 95 per cent with preserved affinity for CD20 antigen. The final preparation was stable up to about 120 h when tested under different conditions. A favourable biodistribution profile was observed with liver showing the maximum uptake of the RIC.
  
  
  CONCLUSIONS
  A favourable radiochemical purity, stability and biodistribution of the radiolabelled immunoconjugate indicate that clinical trials for evaluation of toxicity and efficacy of 177 Lu-DOTA-antiCD20 antibody-Rituximab (BioSim) in patients of relapsed and refractory non Hodgkin's lymphoma can be considered.
authors.forename: Parul
authors.initials: P
authors.lastname: Thakral
authors.forename: Suhas
authors.initials: S
authors.lastname: Singla
authors.forename: Madhav Prasad
authors.initials: MP
authors.lastname: Yadav
authors.forename: Atul
authors.initials: A
authors.lastname: Vasisht
authors.forename: Atul
authors.initials: A
authors.lastname: Sharma
authors.forename: Santosh Kumar
authors.initials: SK
authors.lastname: Gupta
authors.forename: C S
authors.initials: CS
authors.lastname: Bal
authors.affiliation: Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Arun
authors.initials: A
authors.lastname: Malhotra
mesh_terms: D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry / Q000627:therapeutic use*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry / Q000627:therapeutic use*; D007194:India; D008187:Lutetium / Q000737:chemistry / Q000627:therapeutic use*; D016393:Lymphoma, B-Cell / Q000532:radiotherapy*; D016499:Radioimmunotherapy / Q000379:methods*; D011868:Radioisotopes / Q000737:chemistry / Q000627:therapeutic use*; D000069283:Rituximab
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D018796:Immunoconjugates; D011868:Radioisotopes; D000069283:Rituximab; D008187:Lutetium