Caribou Biosciences : CB-012 AMpLify Study Trial Design ASCO 2024

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Abstract TPS6586

A first-in-human Phase 1, multicenter, open-label study of CB-012, a next-generation

CRISPR-edited allogeneic anti-CLL-1CAR-T cell therapy for adults with relapsed/refractory acute myeloid leukemia (AMpLify)

Naval G. Daver,1 Abhishek Maiti,1 David A. Sallman,2 Gail J. Roboz,3 Melhem M. Solh,4 Filippo Milano,5 Stephen A. Strickland,6 Alireza Eghtedar,7 Steven B. Kanner,8 Guy Ledergor,8 Donna Marcy,8 Elizabeth Garner,8

Brian J. Francica,8 McKay Shaw,8 Kalin Bird,8 Enrique Zudaire,8 Socorro Portella,8 Pankit Vachhani,9 Jae H. Park10

1MD Anderson Cancer Institute, Houston, Texas, USA; 2Moffitt Cancer Center, Tampa, FL, USA; 3Weill Cornell Medicine and The New York Presbyterian Hospital, New York, New York, USA; 4The Bone Marrow and Transplant Group of Georgia, Atlanta, Georgia, USA;

5Fred Hutchinson Cancer Center, Seattle, Washington, USA; 6SCRI at TriStar Centennial, Nashville, Tennessee, USA; 7The Colorado Blood Cancer Institute, Denver, Colorado, USA; 8Caribou Biosciences, Inc., Berkeley, California, USA;

9University of Alabama at Birmingham, Birmingham, Alabama, USA; 10Memorial Sloan Kettering Cancer Center, New York, New York, USA

.

Background

• In acute myeloid leukemia (AML), a challenge in the development of CAR-T cell therapies has been the limitation of suitable target antigens since many are also expressed on hematopoietic stem cells and progenitor cells (HSPCs)
• C-typelectin-likemolecule-1(CLL-1) has emerged as an attractive therapeutic target due to its expression on AML mature blasts and leukemic stem cells and its absence on HSPCs1
• CB-012is an allogeneic CAR-T cell therapy that targets CLL-1
• In murine xenograft models of AML, CB-012 significantly reduced tumor burden and increased the survival of mice bearing CLL-1+ tumors2

1. Daver N, et al. Leukemia, 2021;35(7):1843-1863.https://doi.org/10.1038/s41375-021-01253-x.
2. Francica B, et al. 2024 American Association for Cancer Research Annual Meeting; April 9, 2024; San Diego, CA. Abstract 6323. https://investor.cariboubio.com/static-files/306bbc8d-d94f-461a-847d-1d426cf76e8f.

AMpLify trial objectives

Dose Escalation (Phase 1, Part A)	Dose Expansion (Phase 1, Part B)
• Primary Objectives:	• Primary Objectives:
- Safety and tolerability of CB-012 therapy in patients with r/r AML	- Antitumor response of CB-012 in patients with r/r or
(de novo or secondary)	MRD-positive AML
- MTD and/or RDE	• Secondary Objectives:
• Secondary Objectives:	- Efficacy of CB-012 in patients with r/r or MRD-positive AML
- PK/PD of CB-012	- Safety and tolerability of CB-012 therapy in patients with r/r or
- Preliminary antitumor activity of CB-012	MRD-positive AML
in patients with r/r or MRD-positive AML	- PK/PD of CB-012

CB-012:anti-CLL-1 allogeneic CAR-T cell therapy

with a PD-1 knockout and immune cloaking

				4		Armored with 5 genome edits
				KO	1	TRAC gene knockout (KO)
					• Eliminates TCR expression, reduces GvHD risk
				PD-1 KO
		Anti-			Human anti-CLL-1 CAR site-specifically inserted into TRAC gene
			3	2
		CLL-1		• Eliminates random integration, targets tumor antigen
		CAR		B2M-HLA-E
				5		PD-1 KO for enhanced antitumor activity
	2
TCR		PD-L1	3
KO		CLL-1		• Potentially better therapeutic index via initial tumor debulking
1

4 B2M gene KO

• Reduces HLA class I presentation and T cell-mediated rejection

5	B2M-HLA-E-peptide fusion site-specifically inserted into B2M gene
• Blunts NK cell-mediated rejection
1st CAR-Tcell with checkpoint inhibition and		Cas12a chRDNA editing for	Potent, fully human anti-CLL-1 scFv†
immune cloaking (PD-1 KO, B2M KO +		reduced off-target editing and
	with a CD28 costimulatory domain
B2M-HLA-E-peptide fusion) to enter the clinic*		enhanced insertion rates

* To company's knowledge

• Anti-CLL-1-specificscFv exclusively licensed from Memorial Sloan Kettering Cancer Center for allogeneic cell therapies

CB-012 significantly reduced tumor burden and increased overall survival in preclinical studies

AMpLify key inclusion criteria

• r/r AML that failed standard treatment or MRD-positive AML with lack of	• ECOG performance status of 0 or 1
effective treatment options plus any of the following criteria:	• Clinical laboratory values during screening:
- Relapsed AML*	- AST and ALT ≤ 3.0 × ULN
- Refractory AML, defined as having not achieved a first CR after 2 cycles	- Total bilirubin ≤ 2.0 × ULN‡
of intensive induction chemotherapy†	- Creatinine clearance ≥ 45 mL/min/1.73 m2
- MRD-positive AML in CR after prior relapse, regardless of risk criteria*
- MRD-positive AML in first CR*
• Nonproliferative disease
• Suitable candidate for allogeneic SCT with an identified donor
• ≤ 3 prior lines of therapy and ≤ 2 allogeneic SCTs
* Per European LeukemiaNet 2022

• Such as 7 + 3 or 5 + 2 or similar regimen, 1 cycle of FLAG-Ida or CLIA or CLAG-M or similar purine analogue containing induction, or 2 cycles combining venetoclax with either a hypomethylating agent or low-dose cytarabine
  ‡ Except in patients with congenital hyperbilirubinemia (e.g., Gilbert syndrome)

AMpLify key exclusion criteria

• Prior treatment with CAR-T cell therapy directed at any target	• Received any of the following:
• Prior treatment with any CLL-1-directed agent	- Allogeneic SCT within 100 days before lymphodepletion
• Acute promyelocytic leukemia	- Any drug used for GvHD treatment ≤ 4 weeks before CB-012 infusion
- Donor lymphocyte infusion < 30 days prior to lymphodepletion
• Rapidly progressive disease
- Autologous SCT < 6 weeks before lymphodepletion
• Metabolically inactive or isolated extramedullary disease
• Known active CNS involvement or clinical signs of meningeal involvement
• Diagnosed with or treated for invasive malignancy other than AML, except
• Clinically significant stroke or seizure < 6 months of signing informed
for malignancy treated with curative intent and with no known active
consent form
disease present for > 1 year before enrollment
• Seropositive for HIV; active HBV/HCV infection
• Prior antitumor therapy received within 14 days (some exceptions
• Presence of donor-specific(product-specific)anti-HLA antibodies
are allowed)

Overall survival analysis

of survival
Probability	**CB-012 versus
	vehicle p=0.0001

Days post single dose*

Single dose of CB-012significantly reduced tumor burden over a longer duration compared to vehicle treatment in an AML xenograft model

* Orthotopic engraftment of HL-60CLL-1-expressing AML model in NSG mice

• Orthotopic engraftment of U937 CLL-1- and PD-L1-expressing cell line in NSG mice

Overall survival analysis

	Vehicle
survivalof	Control	CAR-T
(4 of 5	CB-012 edits,
	PD-1 unedited)
	CB-012
Probability	**CB-012 versus

control p=0.0001

Days post single dose†

Single dose of CB-012significantly reduced tumor burden over a longer duration compared to control CAR-T cells in an AML xenograft model

AMpLify participating sites

7 active sites

Alabama

University of Alabama at Birmingham

Colorado

Colorado Blood Cancer Institute

Georgia

Blood & Marrow Transplant Group of Georgia

(Northside)

New York

Memorial Sloan Kettering Cancer Center

Tennessee

TriStar Bone Marrow Transplant

Texas

MD Anderson Cancer Center

Washington

CB-012 AMpLify Phase 1 trial design

Dose escalation underway

Patients with r/r AML	Part A: 3+3 dose escalation
•	Relapsed or refractory or MRD+ AML patients who have received 1 to 3	•	Objective: safety, determine MTD/RDE
	prior lines of therapy	Part B: dose expansion
•	Patients with prior allo or auto SCT are allowed
•	Objective: antitumor response, determine RP2D, safety
•	Exclusions: prior CAR-T cell therapy and/or CLL-1-targeted therapy

r/r AML

Lymphodepletion CB-012

-5 TO -3 DAYS	DAY 0	28 DAYS	3 MONTHS	6 MONTHS	9 MONTHS	12 MONTHS*
							Safety and tolerability
							Response assessment
Cyclophosphamide
(750 mg/m²/d)	SINGLE
Fludarabine	DOSE
(30 mg/m²/d)							Planned enrollment: ~70 patients
		Dose level 1: 25x106 CAR-T cells (enrolling patients)
NCT06128044

Fred Hutchinson Cancer Center

Additional sites planned

AMpLify Phase 1 clinical trial summary

• Allogeneic CAR-T cell therapy is an investigational treatment that may address the unmet needs of r/r AML patients
• CB-012is an allogeneic anti-CLL-1CAR-T cell therapy derived from healthy donor T cells and engineered using Cas12a chRDNA technology
• To our knowledge, CB-012 is the first allogeneic CAR-T cell therapy being studied in a clinical trial for r/r AML that is designed to improve antitumor activity through:
• • Checkpoint disruption via PD-1 knockout to reduce T cell exhaustion and
  • An immune cloaking strategy with a B2M knockout and insertion of a B2M-HLA-E fusion protein to blunt immune- mediated rejection
• AMpLify is a Phase 1 first-in-human trial investigating the safety and efficacy of CB-012 as a single infusion in patients with r/r AML at clinical sites across the United States

Patient enrollment is ongoing in dose escalation of the AMpLify trial

* Additional follow-up scheduled for months 13-24 at longer intervals	Contact: [e-mail]

ABBREVIATIONS	CORRESPONDING AUTHOR	American Society of Clinical Oncology Annual Meeting
ALT: alanine aminotransferase; AML: acute myeloid leukemia; AST: aspartate aminotransferase; B2M: β2-microglobulin;CAR: chimeric antigen
Naval G. Daver, MD ([e-mail])	Hematologic Malignancies-Leukemia, Myelodysplastic Syndromes, and Allotransplant
receptor; chRDNA: CRISPR hybrid RNA-DNA;CLAG-M: cladribine, cytarabine, granulocyte colony-stimulating factor, mitoxantrone; CLIA: cladribine,
The University of Texas MD Anderson Cancer	June 3, 2024 - Chicago, IL
idarubicin, cytarabine; CLL-1:C-typelectin-likemolecule-1;CNS: central nervous system; CR: complete remission; ECOG: Eastern Cooperative
Oncology Group; FLAG-Ida: fludarabine, cytarabine, granulocyte colony-stimulating factor, idarubicin; GvHD: graft-versus-host disease; HBV: hepatitis	Center, Houston, TX
B virus; HCV: hepatitis C virus; HIV: human immunodeficiency virus; HLA: human leukocyte antigen; HSPCs: hematopoietic stem cells and progenitor
cells; KO: knockout; MRD: measurable residual disease; MTD: maximum tolerated dose; NK: natural killer; PD: pharmacodynamics; PK:
pharmacokinetics; RDE: recommended dose for expansion; RP2D: recommended Phase 2 dose; r/r: relapsed/refractory; SCT: stem cell
transplantation; TCR: T cell receptor; ULN: upper limit of normal.

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