An Open-label Phase II Study of Lorvotuzumab Mertansine

Study Treatment:

If you are found to be eligible to take part in this study, you will receive lorvotuzumab by
vein on Days 1 and 8 (+/- 2 days) of each cycle. It may take a few minutes or several hours
to receive the study drug. Your doctor will discuss this with you.

All treatments with IMGN901 must be administered at MD Anderson.

Each cycle is 21 days (+/-6 days). However, they may be longer or shorter depending on if/how
the disease responds to the treatment, how your bone marrow reacts to treatment, and what the
doctor thinks is in your best interest.

Your dose of lorvotuzumab may be raised, lowered, and/or delayed if the doctor thinks it is
in your best interest.

Study Visits:

On Day 1 of each cycle, you will have a physical exam.

One (1) time each week during the first 4 cycles, blood (about 1 tablespoon) will be drawn
for routine tests. After Cycle 4, you will have these blood draws 1 time every 2-4 weeks. If
your doctor thinks it is needed, more blood may need to be drawn. The study doctor or study
staff will discuss this with you if more blood is needed.

During the first cycle, all the laboratory evaluations will be done at MD Anderson. After
Cycle 1, you may be able to have these blood draws performed at a local lab or clinic that is
closer to your home, and the results reported to the research nurse of the study at MD
Anderson. The study doctor or study staff will discuss this option with you. The results of
these blood draws will be sent to the study doctor for review.

On Day 21 of Cycle 1 (+/- 7 days), then every 1-3 cycles after that, you will have a bone
marrow aspiration/biopsy to check the status of the disease. If the doctor thinks it is
needed, these may be done more or less often, depending on your response to the study drug.

You will have blood draws and/or bone marrow aspirations at any time that the doctor thinks
it is needed while you are on study.

If you stay on study for more than 6 months and you are not having side effects, you may have
some of the above tests more or less frequently. For example, you may only have a bone marrow
aspiration 1 time every 6-12 months and blood draws 1 time each cycle. The study doctor will
discuss this with you.

Length of Study:

You may take up to 12 cycles of lorvotuzumab. If the doctor thinks it is in your best
interest, you may be able to continue receiving the study drug beyond Cycle 12. You will no
longer be able to take the study drug if the disease gets worse, if intolerable side effects
occur, or if you are unable to follow study directions.

Your participation on the study will be over after follow-up.

End-of-Study Visit:

If you leave the study before the end of Cycle 12, within 30 days (+/- 7 days) after the last
dose of study drug:

- Blood (about 2-3 tablespoons) will be drawn for routine tests.

- If the doctor thinks it is needed, you will have a bone marrow aspirate/biopsy to check
the status of the disease.

Long Term Follow-Up:

If the disease appears to get better and you are responding well to the study drug, you will
return to MD Anderson every 3-6 months for up to 5 years after your last dose of study drug
for the study staff to check how you are doing.

If you cannot return to MD Anderson for these visits, you may be called by a member of the
study staff. The call should last about 10 minutes.

This is an investigational study. Lorvotuzumab is not FDA approved or commercially available.
It is currently being used for research purposes only. The study doctor can explain how the
drug is designed to work.

Up to 60 participants will take part in this study. All will be enrolled at MD Anderson.

Inclusion Criteria:

1. Patients with CD56 expressing hematological malignancy, as follows: Cohort 1: CD56
expressing hematological malignancies including but not limited to AML, high-risk
myelodysplastic syndrome (MDS), natural-killer leukemia, acute lymphoblastic leukemia,
accelerated and blast-phase chronic myelocytic leukemia (CML) who have failed prior
therapy or for which no standard therapy exists.Cohort 2: Patients with MF (either
primary MF, post-polycythemia MF, or post-essential thrombocythemia MF) and CD56
expression who have been on ruxolitinib or JAK-inhibitor therapy for at least 12 weeks
and deemed refractory or sub-optimal responders in the opinion of the treating
physician.Cohort 3: Patients with pathological diagnosis of BPDCN with CD56 expression
(frontline and relapsed/refractory).

2. Any level of CD56 expression will be considered sufficient for enrollment on this
study.

3. Prior therapy with hydroxyurea, chemotherapy, biological or targeted therapy (e.g.
FLT3 inhibitors, other kinase inhibitors), or hematopoietic growth factors is allowed.

4. Age >/=18 years

5. Eastern Cooperative Oncology Group (ECOG) Performance Status
6. Adequate organ function: total bilirubin ( aspartate aminotransferase (AST) or alanine aminotransferase (ALT) 5.0 x ULN if considered to be due to leukemic involvement); serum creatinine ULN, amylase and lipase
7. In the absence of rapidly progressing disease and after discussion with the Principal
Investigator (PI), the interval from prior treatment to time of IMGN901 administration
will be at least 2 weeks or at least 5 half-lives for cytotoxic/noncytotoxic agents.
The half-life be based on published pharmacokinetic literature (abstracts,
manuscripts, investigator brochure's, or drug-administration manuals) and will be
documented in the protocol eligibility document.

8. continuation from criteria #7: For prior monoclonal antibody therapy the interval from
prior monoclonal antibody treatment to time of IMGN901 administration will be at least
2 weeks. The use of chemotherapeutic or anti-leukemic agents other than hydroxyurea
(as defined in the protocol) is not permitted during the study with the exception of
intrathecal (IT) therapy for patients with controlled CNS leukemia at the discretion
of the PI. Hydroxyurea is allowed prior to the initiation of IMGN901 and during the
first 3 cycles, either prior to or concomitantly with IMGN901 administration initially
to control Leukocytosis.

9. Women of childbearing potential must practice contraception. Females of childbearing
potential: Recommendation is for 2 effective contraceptive methods during the study.
Adequate forms of contraception are double barrier methods (condoms with spermicidal
jelly or foam and diaphragm with spermicidal jelly or foam), oral, depo provera, or
injectable contraceptives, intrauterine devices, and tubal ligation. Male patients
with female partners who are of childbearing potential: Recommendation is for male and
partner to use at least 2 effective contraceptive methods, as described above, during
the study.

10. Females must be surgically or biologically sterile or postmenopausal (amenorrheic for
at least 12 months) or if of childbearing potential, must have a negative serum or
urine pregnancy test within 72 hours before the start of the treatment

11. Patients must provide written informed consent.

12. Women of childbearing potential must agree to use an adequate method of contraception
during the study and until 3 months after the last treatment. Males must be surgically
or biologically sterile or agree to use an adequate method of contraception during the
study until 3 months after the last treatment. Adequate methods of contraception
include: Total abstinence when this is in line with the preferred and usual lifestyle
of the patient. Periodic abstinence (e.g., calendar, ovulation, symptothermal,
post-ovulation methods) and withdrawal are not acceptable methods of contraception.
Female sterilization (have had surgical bilateral oophorectomy with or without
hysterectomy) or tubal ligation at least six weeks before taking study treatment. In
case of oophorectomy alone, only when the reproductive status of the woman has been
confirmed by follow up hormone level assessment Male sterilization (at least 6 months
prior to screening).

13. continued from criteria #12: For female patients on the study, the vasectomized male
partner should be the sole partner for that patient Combination of any of the two
following (a+b or a+c or b+c) Use of oral, injected or implanted hormonal methods of
contraception or other forms of hormonal contraception that have comparable efficacy
(failure rate <1%), for example hormone vaginal ring or transdermal hormone
contraception Placement of an intrauterine device (IUD) or intrauterine system (IUS)
Barrier methods of contraception: Condom or Occlusive cap (diaphragm or cervical/vault
caps) with spermicidal foam/gel/film/cream/ vaginal suppository In case of use of oral
contraception, women should have been stable on the same pill before taking study
treatment. Note: Oral contraceptives are allowed but should be used in conjunction
with a barrier method of contraception due to unknown effect of drug-drug interaction

14. continued from criteria #13 Women are considered post-menopausal and not of child
bearing potential if they have had 12 months of natural (spontaneous) amenorrhea with
an appropriate clinical profile (e.g. age appropriate, history of vasomotor symptoms)
or have had surgical bilateral oophorectomy (with or without hysterectomy) or tubal
ligation at least six weeks ago. In the case of oophorectomy alone, only when the
reproductive status of the woman has been confirmed by follow up hormone level
assessment is she considered not of child bearing potential.

Exclusion Criteria:

1. Patients with known allergy or hypersensitivity to IMGN901.

2. Patients who have previously been treated with IMGN901.

3. Patients with symptomatic central nervous system (CNS) leukemia or patients with
poorly controlled central nervous system leukemia.

4. Peripheral neuropathy >grade 2.

5. Active or clinically symptomatic chronic pancreatitis or disease affecting pancreas.

6. Neurologic disease including multiple sclerosis, Eaton-Lambert syndrome,
demyelination.

7. Significant cardiac disease including myocardial infarction or unstable angina within
6 months, uncontrolled hypertension despite medical therapy (defined as blood pressure
>160/110 in spite of adequate medical therapy), active and uncontrolled congestive
heart failure New York Heart Association (NYHA) class III/IV, stroke within preceding
6 months.

8. Patients with known Human Immunodeficiency Virus seropositivity will be excluded.

9. Known to be positive for hepatitis B by surface antigen expression. Known to have
active hepatitis C infection (positive by polymerase chain reaction or on antiviral
therapy for hepatitis C within the last 6 months). Known to be active CMV infection or
herpes zoster infection.

10. Pregnant or breast feeding (lactating) women, where pregnancy is defined as the state
of a female after conception and until the termination of gestation, confirmed by a
positive B-human chorionic gonadotropin (HCG) laboratory test.

11. Patients with any concurrent severe and/or uncontrolled medical condition or active
uncontrolled systemic infection as determined by the investigator.

12. Patients who have had any major surgical procedure within 14 days of Day 1.

13. Patients unwilling or unable to comply with the protocol.