Protocol 260

Inclusion Criteria:

- Subjects must be 18 to 70 years of age inclusive

- If female and of child-bearing age, subjects must be non-pregnant, not breast
feeding, and use adequate contraception. Males must use adequate contraception.

- Subject must have newly diagnosed, Grade II-IV acute GVHD requiring therapy. Biopsy
for confirmation of GVHD is not mandatory, but is recommended when feasible.
Enrollment should not be delayed awaiting biopsy results.

- Subject must have received either full or reduced intensity myeloablative regimens
followed by an allogeneic hematopoietic stem cell transplant using bone marrow,
peripheral blood stem cell, or cord blood, including DLI

- Subjects must have minimal renal and hepatic function as defined by:

* Calculated creatinine clearance (CLcr) of > 30 mL/min using the Cockroft-Gault
equation

- Subject must be available for all specified assessments at the study site through
study Day 28.

- Subjects must provide written informed consent and authorization for use and
disclosure of protected health information (PHI).

Protocol 260 Exclusion Criteria:

- Subject has received previous treatment for Grade II-IV acute GVHD (except as noted
in criterion 2).

- Subject has been treated for GVHD with methylprednisolone, > 2mg/kg/day, for more
than 72 hours prior to receiving Prochymal™

- Subject has uncontrolled alcohol or substance abuse within 6 months of randomization.

- Subject has received an investigational agent (not approved by FDA for marketed use
in any indication) within 30 days of randomization. Subjects may not receive an
investigational agent during the 28-day study period

- Subject has any underlying or current medical or psychiatric condition that, in the
opinion of the Investigator, would interfere with the evaluation of the subject
(e.g., uncontrolled infection, right heart failure, pulmonary hypertension, etc.)

- Subject has unstable arrhythmia

- Subject is unwilling to sign consent form for the long-term follow-up study, protocol
No. 261

- Subject has a known allergy to bovine or porcine products.

- Subject had received transplant for a solid tumor disease.

Protocol 261

Inclusion Criteria:

- Subject must have received any treatment with the Investigational Agent in the
preceding Prochymal® study.

- Subject must have completed their participation in a preceding Prochymal® study.

- If female and of child-bearing age, subjects must be non-pregnant, not
breast-feeding, and use adequate contraception. Male subjects must use adequate
contraception.

- Subject must provide written informed consent and written authorization for
disclosure and use of PHI.