Inclusion Criteria:

1. Age 18 and above

2. Patients with histologically confirmed DLBCL, including primary mediastinal large B
cell lymphoma, T cell rich B cell lymphoma, "double hit" DLBCL, mantle cell lymphoma,
any transformed low grade B cell lymphomas or grade 3 follicular lymphoma (Grade 3a
or 3b) who were refractory to RCHOP-like or any anthracycline based chemotherapy or
relapsed after at least one prior combination chemotherapeutic regimen and who are
deemed candidates for a salvage type chemotherapy.

- Relapsed disease:

- Progressive disease after a CR for at least 28 days. Progression will be defined
according to the Revised Response Criteria for Malignant Lymphoma (Cheson 2007
(33)).

- Refractory disease (Subjects must meet one of the following criteria):

- Persistent or progressive lymphoma with a CR of <28 days duration or with a PR
of any duration. Subjects must have received at least 3 cycles of RCHOP-like or
any anthracycline base chemotherapy or at least 2 full cycles of HyperCVAD-like
chemotherapy.

- Persistent lymphoma and stable disease after at least 2 cycles of RCHOP-like or
any anthracycline base chemotherapy or at least 1 full cycle of HyperCVAD-like
chemotherapy (part A and B).

- Progressive disease despite at least 1 cycle of RCHOP-like or any anthracycline
base chemotherapy or at least 1 cycle (part A or A and B) of HyperCVAD-like
chemotherapy.

3. Measurable disease, defined by the revised lymphoma criteria (Cheson 2007).

4. Absolute neutrophil count ≥1,500 and platelet count ≥ 75,000, unless due to
underlying lymphoma.

5. Left ventricular ejection fraction estimated by MUGA scan or 2D-echocardiogram of at
least 45% Cardiology consult is recommended prior to enrollment if a history of
coronary artery disease, CHF with estimated LVEF of <50% or clinically significant
arrhythmia.

6. Estimated glomerular filtration rate (GFR) must be ≥ 50 mL/min

7. Serum bilirubin ≤ 1.5 × upper limit of normal (ULN) unless deemed elevated secondary
to lymphoma involvement of the liver or known Gilbert's syndrome.

8. Aspartate transaminase (AST)/alanine transaminase (ALT) ≤ 2.5 × ULN; unless elevated
secondary to lymphoma involvement of the liver

9. Alkaline phosphatase ≤ 2.5 × ULN; unless elevated secondary to lymphoma involvement
of the liver.

10. Performance status of ECOG 0-2.

11. Both potentially AutoSCT or AlloSCT candidates and those who are not transplant
candidates are eligible for the study.

12. Capable of understanding the investigational nature, potential risks and benefits of
the study, and able to provide valid informed consent and HIPAA consent.

13. Female patients of childbearing potential must have a negative serum pregnancy test
within 3 days prior to enrollment.

14. Male and female patients of reproductive potential must use an effective
contraceptive method during the study and for a minimum of 1 year after the after
study treatment.

15. Must be able to comply with study and follow up requirements.

Exclusion Criteria:

1. Current concomitant chemotherapy, radiation therapy, or immunotherapy other than as
specified in the protocol.

2. Use of investigational agents within 4 weeks prior to enrollment.

3. Any anticancer therapy within 3 weeks before study entry. The patient must have
recovered from all acute toxicities from any previous therapy.

4. Radioimmunotherapy (i.e. Zevalin) within 8 weeks of enrollment.

5. Prior treatment with anti-CD20 monoclonal antibody or alemtuzumab within 4 weeks
prior to start of therapy.

6. Autologous stem cell rescue within 12 weeks before study enrollment or those who
underwent allogeneic stem cell transplant within one year of enrolment.

7. Clinically significant cardiac disease including unstable angina, acute myocardial
infarction within six months prior to therapy, congestive heart failure (NYHA
III-IV).

8. Known leptomeningeal or parenchymal brain involvement with lymphoma unless in
complete remission after treatment for at least 12 weeks with negative CSF cytology
within 2 weeks. Prophylaxis of CNS disease using intrathecal dosing of cytotoxic
regimens is permitted and should be performed according to the discretion of the
treating physician.

9. History of serious organ dysfunction or disease involving the heart, kidney, liver or
other organ system that may place the patient at undue risk to undergo treatment.

10. Systemic fungal, bacterial, viral, or other infection if not controlled. Defined as
exhibiting ongoing signs/symptoms related to the infection and without improvement,
despite appropriate antibiotics or other treatment. (May be enrolled if controlled
on treatment).

11. Significant concurrent disease, illness, or psychiatric disorder that would
compromise patient safety or compliance, interfere with consent, study participation,
follow up, or interpretation of study results.

12. Subjects who have current active hepatic or biliary disease (with exception of
patients with Gilbert's syndrome, asymptomatic gallstones, liver metastases or stable
chronic liver disease per investigator assessment)

13. History of significant cerebrovascular disease in the past 6 months or ongoing event
with active symptoms.

14. Clinically significant cardiac disease including unstable angina, acute myocardial
infarction within six months prior to randomization, congestive heart failure (NYHA
III-IV), and arrhythmia unless controlled by therapy, with the exception of
extrasystoles or minor conduction abnormalities.

15. Other malignancy, unless the patient has been disease-free for at least 3 years
following the completion of curative intent therapy, with the following exceptions:
treated non-melanoma skin cancer, any in situ carcinoma, or cervical intraepithelial
neoplasia, regardless of the disease-free duration, are eligible for this study if
definitive treatment for the condition has been completed. Organ-confined prostate
cancer with no evidence of recurrent or progressive disease based on
prostate-specific antigen (PSA) values are also eligible for this study if hormonal
therapy has been initiated, or radical prostatectomy or definitive prostate
irradiation has been performed.

16. Positive test for the Human Immunodeficiency Virus (HIV), unless undetectable viral
load within 3 months of enrollment (HIV RNA less than 48 copies/mL) on HAART therapy.

17. Positive serology for Hepatitis B (HB) defined as a positive test for HBsAg. .
Patients with prior history of Hepatitis B infection, but immune, with only IgG
Hepatitis core antibody + (HBcAb +) must be checked for hepatitis B virus titers by
PCR and if the viral load is undetectable may be enrolled. These patients must
receive anti-viral prophylaxis, such as lamivudine 100 mg po daily (or an equivalent)
starting at least one week prior to cycle 1 and continued through the completion of
treatment and for 9 months after the last dose of ofatumumab. Hepatitis B virus
titers by quantitative PCR and HBsAg should be checked every month (+/- 1 week) while
on therapy and every 3 months (+/- 1 month) thereafter for 9 months after the last
ofatumumab dose. In the event of an early termination of the clinical trial for any
reason, a treating physician will be determining the frequency and the length of
follow up studies of hepatitis B virus titers and HBsAg status. It is recommended
that the patient remains on prophylactic lamivudine or an equivalent, as above,
regardless of whether the study was continued or terminated. In addition, if
appropriate consultation with a hepatologist should be obtained.

18. Positive serology for hepatitis C (HC) defined as a positive test for HCAb if
confirmed by HC RIBA immunoblot assay (for positive HCAb reflexively perform a HC
RIBA immunoblot assay on the same sample)

19. Pregnant or lactating women.