The present invention relates to a new generation of chimeric antigen receptors (CAR), under single-chain or multi-chain forms, the specificity of which, to a desired antigen, is conferred by a VNAR polypeptide derived from monomeric antibodies from cartilaginous fish. Such CARs, which aim to redirect immune cell specificity toward selected undesired malignant cells, are compact and thus particularly adapted to target hollow antigens such as ions channels of efflux pumps present at the surface of drug-resistant cells. The invention encompasses the polynucleotides, vectors encoding said multi-chain CAR and the isolated cells expressing them at their surface, in particularly for their use in immunotherapy.