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.