Inclusion Criteria:

- Histologically documented aggressive systemic mastocytosis or mast cell leukemia +
AHNMD, regardless of the presence of absence of the D816V c-kit mutation, or the
FIP1L1-PDGFR alpha fusion.

- Tissue for evaluation of KIT mutation status of the tumor cells must be collected and
availability confirmed by PI within 6 months prior to entry into study (e.g.
wild-type, D816V, or other KIT mutation). Patients who have systemic mastocytosis
with eosinophilia and known positivity for the FIP1L1-PDGFR alpha fusion are also
eligible only if they have demonstrated relapse or disease progression on prior
imatinib therapy.

- Karnofsky performance status of >30%.

- Liver enzyme values within normal limits unless the sole cause of liver elevation is
due to ASM/MCL. Else, patients must have the following laboratory values: AST and
ALT <= 4X ULN, and/or bilirubin <= 4X ULN if elevation of liver enzymes is considered
solely due to ASM/MCL.

- Serum creatinine <2.0 mg/dL

- For patients with grade >2 blood values, the screening bone marrow exam (e.g.
presence of mast cell infiltrate as defined in Appendix B) and/or the presence of
disease-related hypersplenism should establish that the likely causes of these
cytopenia(s) is related to ASM/MCL.

- No clinical or radiographic (by PA and lateral chest x-ray) evidence of active
pulmonary disease which is considered by the investigator to be unrelated to
mastocytosis.

- Patient must give written informed consent.

Exclusion Criteria:

- Female patients who are pregnant or breast-feeding, or any adult, male or female, of
reproductive potential not agreeing to employ barrier contraceptives throughout the
study.

- Women of childbearing potential must have a negative serum pregnancy test 48 hours
prior to administration of study drug, are required to use barrier contraception for
the duration of the study and for 3 months post study because of the long half life
of the metabolite, CGP52421, and must avoid breast-feeding.

- Any other known disease, concurrent severe and/or uncontrolled medical condition
(e.g. uncontrolled diabetes, cardiovascular disease including congestive heart
failure, myocardial infarction within 6 months, any Grade 3/4 cardiac problems as
defined by the New York Heart Association Criteria and poorly controlled
hypertension, chronic renal disease, active uncontrolled infection) which could
compromise participation in the study.

- Known confirmed diagnosis of HIV infection or active viral hepatitis.

- Patients who have received any investigational agent, chemotherapy, or
2-chlorodeoxyadenosine (2-CdA) within 30 days prior to Day 1 of PKC412 treatment.

- Patients who have received interferon-alpha within 30 days prior to Day 1 of PKC412
treatment.

- Patients who have received hematopoietic growth factor support within 14 days of Day
1 of PKC412 treatment.

- Glucocorticoids should be tapered off within 14 days of Day 1 of PKC412 treatment if
it is anticipated that patients can be tapered off these drugs. Otherwise, for
glucocorticoid-requiring patients, investigators should attempt to taper to the
minimal dose possible at the time of PKC412 start on day 1.

- Patients who have had any surgical procedure, excluding central venous catheter
placement or other minor procedures (e.g. skin biopsy) within 14 days of Day 1 of
PKC412 treatment.

- Patients unwilling or unable to comply with the protocol.

- Patients with known malignant disease involving the central nervous system.

- Patient with any pulmonary infiltrate or abnormality on the baseline chest X-ray
known to be new in the previous 4 weeks. However, if a patient has a pleural
effusion which is considered related to systemic mastocytosis (e.g. secondary to
ascites) and not causing symptomatic respiratory complaints, the patient may be
eligible after discussion with the sponsor.