Inclusion Criteria:

- Signed written informed consent according to IGH/EU/GCP and national local laws.

- Age 18-60 years.

- ALL with B-/T-precursor phenotype refractory to first line therapy.

- ALL with B-/T-precursor phenotype 1st isolated bone marrow relapse, occurring < 24
months from the achievement of first CR, after chemotherapy or hematopoietic
stem-cell transplantation (HSCT) defined as follows:

* ≥ 5% leukemic blasts in the bone marrow not attributable to another cause (e.g.
marrow regeneration); if there are no circulating blasts and the bone marrow contain
5-20% leukemic blasts, a repeat bone marrow performed at least a week later is
necessary to confirm relapse.

- ECOG performance status 0-2 or reversible ECOG 3 score following intensive care of
complications.

- Adequate hepatic and renal function, unless considered due to organ leukemic
involvement:

- Serum creatinine <1.5 mg/dl; if serum creatinine >1.5 mg/dl, then the estimated
glomerular filtration rate (GFR) must be > 60 mL/min/1.73 m2 as calculated by
the Modification of Diet in Renal Disease equation where Predicted GFR
(ml/min/1.73 m2) = 186 x (Serum Creatinine)-1.154 x (age in years)-0.023 x
(0.742 if patient is female), x (1.212) if patient is black.

- Serum bilirubin ≤ 1.5 x upper limit of normal (ULN).

- Aspartate transaminase (AST)/alanine transaminase (ALT) ≤ 2.5 x ULN.

- Alkaline phosphatase ≤ 2.5 x ULN.

Exclusion Criteria:

- Prior exposure to Clofarabine or, in primary refractory patients only, to
Cyclophosphamide during induction courses.

- Patients relapsed > 24 months from first CR. - Philadelphia chromosome-positive (Ph+)
ALL.

- Diagnosis of Burkitt-type/B-ALL, or B-/T-lymphoblastic lymphoma with < 25% bone
marrow involvement.

- Concurrent or isolated central nervous system (CNS) relapse.

- Pre-existing, uncontrolled pathology such as cardiac disease (congestive/ischemic,
acute myocardial infarction within the past 3 months, untreatable arrythmias, NYHA
classes III and IV).

- Severe neurological or psychiatric disorder that impairs the patient's ability to
understand and sign the informed consent, or to cope with the intended treatment
plan.

- Active uncontrolled systemic fungal, bacterial, viral, or other infection (defined as
exhibiting ongoing signs/symptoms related to the infection and without improvement,
despite appropriate antibiotics or other treatment).

- HIV positive serology or active hepatitis infection. - Concurrent diagnosis of active
cancer requiring concurrent chemotherapy and/or radiotherapy, and/or with life
expectancy < 1 year.

- Patients who are pregnant or adults of reproductive potential not employing an
effective method of birth control (women of childbearing potential must have a
negative serum pregnancy test within 48 hrs prior to administration of
Clofarabine-Cyclophosphamide). Post menopausal women must be amenorrheic for at least
12 months to be considered of non-childbearing potential. Male and female patients
must agree to employ an effective barrier method of birth control throughout the
study and for up to 3 months following discontinuation of study drugs.