A better immunotoxin against cancer

Monoclonal antibodies

V L V H Ck IgG V H V L Gets cancer cells to commit suicide Get immune system to kill cancer cells Examples: Rituximab, Alemtuzumab, Herceptin

Radiolabeled Monoclonal antibodies

V L V H Ck IgG V H V L Targets radiation to the cancer cell Examples: Zevalin, Bexxar

Immunotoxins

V L V H Ck IgG V H V L Inhibition of protein synthesis Cell death TOXIN

RECOMBINANT IMMUNOTOXINS

V L V H Ck RFB4 V H V L V L -s-s V H C 3 II BL22 Ib Ia II PE Ib III III

CD22 II BL22 II III V L -s-s V H II III RFB4(dsFv)-PE38 (BL22) III III II III REDL S S Ia III REDL II Ia COATED PIT ENDOSOMES III REDL II H GOLGI III II PE38 ER Ia II III PSEUDOMONAS EXOTOXIN III II III II III II EF2 III II SHUTTLE KDEL RECEPTOR CYTOSOL

HAIRY CELL LEUKEMIA

B-cell leukemia 2% of all Leukemias Low blood counts Splenomegaly (large spleen) Cytoplasmic projections

Treatment of HCL

Cladribine (CdA) and Pentostatin (DCF) can induce long term CRs but have not been shown to cure the disease. They have decreased efficacy with each repeated course.

Phase I Trial of BL22 in CdA-Resistant HCL Summary

•

Response: Total 31 CR PR CR+PR 19 (61%) 6 (19%) 25 (81%)

•

CR rate 86% at high doses, 41% at low doses

•

Most (11/19) CRs were after just 1 cycle

•

Toxicity: Most commonly temporary fluid retention Kreitman et al., NEJM, 345:241, 2001, Kreitman et al., JCO, 23:6719, 2005

Phase II Trial of BL22 in HCL Results

Retreat 56% CR: Complete remission HR: Hematologic remission (good blood counts) PR: Partial remission (>50% improvement) SD: Stable disease PD: Progressive disease

• •

Conclusions: One cycle highly active Retreatment improved best response

Phase II Disease-free survival

100 80

| | | || | | | | | | |

60 40 20 n=17 (Patients achieving CR) Median CR duration = 31+ (5-59+) mo 12/17 (71%) still in CR 0 0 10 20 30 40 50

Months from beginning BL22

60

Complete remission with BL22 4 3 2 1 0 300 250 200 150 100 50 0 18 16 14 12

C1 C1 C2 Col 4 vs Col 10 C2 C3 C3

ANC PLATELETS HGB ANC PLATELETS HGB 2000 1500 1000 500 0

C1 C2 C3

HCL HCL 0 50 100 150 200 250 300 29003100 DAY OF BL22 PROTOCOL

Resolution of Splenomegaly with BL22

Pre C7D1 (Height = 250 mm) (Height = 125 mm)

CD4 counts in HCL Pre and Post BL22 1000 800 600 400 200 0 Pre Post

Conclusions:

•

Hairy cell leukemia is a chronic leukemia which shows no evidence of cure with standard chemotherapy, so patients who are young may die of this disease without alternative treatment.

•

BL22 is highly active in HCL despite patients not responding to standard HCL therapy.

•

Compared to standard chemotherapy, BL22 is not toxic to normal T-cells and does not even have prolonged damage to normal B-cells.

•

HA22 (CAT-8015), an improved version of BL22, is completing Phase I testing in HCL.

COLLABORATORS: BL22 LMB: IRA PASTAN DAVID J.P. FITZGERALD Q.C. WANG MASANORI ONDA G. SALVATORE B.K. LEE MEDICINE / PED BRANCH: WYNDHAM H. WILSON ALAN WAYNE CLINICAL IMMUNOTHERAPY SECTION, LMB INGER MARGULIES EVGENY ARONS KAKUSHI MATSUSHITA ROBERTA TRAINI TARA SUNUM RAJAT SINGH rIMMUNOTOXIN CLINICAL TEAM (CCR) LINDA ELLISON RAFFIT HASSAN BARBARA DEBORAH MARP FACILITY (DTP): STEVE GIARDINA ELIZABETH MAESTRI DANIEL COFFMAN RITA MINCEMOYER TOBY HECHT SONYA DUKE EMORY: HARRY FINDLEY MedImmune: BOB LECHLEIDER KATHERINE KAUCIC PATHOLOGY: MARYALICE STETLER- STEVENSON ELAINE S. JAFFE MARK RAFFELD PHARMACY: GEORGE GRIMES DAVID KOHLER HEMATOLOGY: PIERRE NOEL, MARGARET RICK, JAY LOZIER

300 200 100 0 3 2 1 0 14 12 10 8 10 5 0 -25

BL22 PATIENT BH20

C1

ANC (Neutrophils) ANC (Neutrophils)

C1

PLATELETS PLATELETS Hemoglobin (Red cells)

C1

Hemoglobin (Red cells)

C1

Hairy cell count Hairy cell count 0 25 50 75 100 500 DAY OF BL22 PROTOCOL 1000