A Phase I Trial of DI-B4 in Patients With Advanced CD19 Positive Indolent B-cell Malignancies

Inclusion Criteria: 1\. Histologically proven relapsed or refractory indolent B-cell lymphoma or chronic lymphocytic leukaemia. Patients must have received at least one line of previous therapy. 2\. CD19 positive malignancy as demonstrated by immunohistochemistry or flow cytometry 3\. Life expectancy of at least 12 weeks 4\. World Health Organisation (WHO) performance status of 0-1 5\. Haematological and biochemical indices within the ranges shown below. These measurements must be performed within one week (Day -7 to Day 1) before the patient commences treatment with DI-B4. Laboratory Test Value required Haemoglobin (Hb) ≥ 9.0 g/dL (red cell support is permissible), Absolute neutrophil count (ANC) ≥1.0 x 10\^9/L (or ≥0.5 x 10\^9/L if bone marrow involvement), Platelet count ≥75 x 10\^9/L (or ≥30 x 10\^9/L if bone marrow involvement), Serum bilirubin ≤1.5 x upper limit of normal (ULN), unless raised due to Gilbert's syndrome in which case up to 3 x ULN is permissible Alanine amino-transferase (ALT) and/or aspartate amino-transferase (AST) ≤ 2.5 x (ULN) unless raised due to hepatic involvement in which case up to 5 x ULN is permissible 6\. 18 years or over 7\. Written (signed and dated) informed consent and be capable of co-operating with treatment and follow-up 8\. Indolent B-cell lymphoma patients only: Patient has either at least one measurable lesion by CT scan (defined as \>1.5 cm in one axis) or in the case of Waldenström's macroglobulinemia, disease must be assessable by the protocol criteria. Exclusion Criteria: 1\. Radiotherapy (except for palliative reasons), endocrine therapy, immunotherapy, chemotherapy or investigational medicinal products during the previous 4 weeks before treatment. 2\. Ongoing toxic manifestations of previous treatments. Exceptions to this are alopecia or certain Grade 1 toxicities, which in the opinion of the Investigator and the Drug Development Office (DDO) should not exclude the patient. 3\. Known to be serologically positive for hepatitis B (unless due to vaccination), hepatitis C or human immunodeficiency virus (HIV). 4\. Patients with clinically active leptomeningeal or central nervous system lymphoma/leukaemia. 5\. Patients with transformed lymphoma from a pre-existing indolent lymphoma. Patients with a previous history of transformation, but on this disease episode have a biopsy proven indolent recurrence may be included. 6\. Patients receiving corticosteroids, except where the patient has been on a stable dose for the preceding seven days. Doses of prednisolone or equivalent \>10 mg daily are not permitted whilst on the study, doses up to 20mg can be taken any time prior to Cycle 1, Day 1 7\. Concurrent congestive heart failure, prior history of class III/ IV cardiac disease (New York Heart Association \[NYHA\]), history of unstable angina pectoris or myocardial infarction up to 1 year prior to patient enrolment into the trial, presence of severe valvular heart disease or presence of a ventricular arrhythmia requiring treatment 8\. Ability to become pregnant (or already pregnant or lactating). However, those female patients who have a negative serum or urine pregnancy test before enrolment and agree to use two highly effective forms of contraception (oral, injected or implanted hormonal contraception and condom, have an intra-uterine device and condom, diaphragm with spermicidal gel and condom) during the trial and for six months afterwards are considered eligible. 9\. Male patients with partners of child-bearing potential (unless they agree to take measures not to father children by using one form of highly effective contraception \[condom plus spermicide\] during the trial and for six months afterwards). Men with pregnant or lactating partners should be advised to use barrier method contraception (e.g. condom plus spermicidal gel) to prevent exposure to the foetus or neonate. 10\. Major thoracic or abdominal surgery from which the patient has not yet recovered. 11\. At high medical risk because of non-malignant systemic disease including active uncontrolled infection. 12\. Is a participant or plans to participate in another interventional clinical trial, whilst taking part in this Phase I study of DI-B4. Participation in an observational trial would be acceptable. 13\. Any other condition which in the Investigator"s opinion would not make the patient a good candidate for the clinical trial.