This is an active treatment, extended access study open solely to those subjects who have successfully completed the Core and Repeat Dosing portions of the MT-3724_NHL_001_US clinical study and who, in the investigator's judgment, (i) have not had progressive disease while on MT-3724 treatment (i.e.; have shown a complete or partial response or stable disease), (ii) have experienced no clinical or laboratory toxicities that would contraindicate further MT-3724 dosing and (iii) have no acceptable and better alternative treatment available to them.