A trispecific killer engager molecule against CLEC12A effectively induces NK-cell mediated killing of AML cells

Abstract

The low five-year survival rate for patients with acute myeloid leukemia (AML), primarily caused due to disease relapse, emphasizes the need for better therapeutic strategies. Disease relapse is facilitated by leukemic stem cells (LSCs) that are resistant to standard chemotherapy and promote tumor growth. To target AML blasts and LSCs using Natural Killer (NK) cells, we have developed a trispecific killer engager (TriKE™) molecule containing a humanized anti-CD16 heavy chain camelid single domain antibody (sdAb) that activates NK cells, an IL-15 molecule that drives NK cell priming, expansion and survival, and a single-chain variable fragment (scFv) against human CLEC12A (CLEC12A TriKE). CLEC12A is a myeloid lineage antigen that is highly expressed by AML cells and LSCs, but not expressed by normal hematopoietic stem cells (HSCs), thus minimizing off-target toxicity. The CLEC12A TriKE induced robust NK cell specific proliferation, enhanced NK cell activation and killing of both AML cell lines and primary patient derived AML blasts in vitro while sparing healthy HSCs. Additionally, the CLEC12A TriKE was able to reduce tumor burden in pre-clinical mouse models. These findings highlight the clinical potential of the CLEC12A TriKE for the effective treatment of AML.

Bimodal expression of potential drug target CLL‐1 (CLEC12A) on CD34+ blasts of AML patients

“… 13 , 16 , 19 , 20 , 21 Based on these studies, various CLL‐1‐targeted therapies are being developed and tested in clinical trials. 22 , 23 , 24 , 25 , 26 , 27 , 28 In this study, we observed various bimodal expression patterns of CLL‐1 in AML patient samples (Figure 1 A‐C). The bimodal expression can be identified as two distinct (positive vs. negative) populations within the CD34 + AML blasts.…”

“…Moreover, within the CLL‐1‐positive blasts, only unimodal expression of CLL‐1 was identified 13,16,19‐21 . Based on these studies, various CLL‐1‐targeted therapies are being developed and tested in clinical trials 22‐28 . In this study, we observed various bimodal expression patterns of CLL‐1 in AML patient samples (Figure 1A‐C).…”

Natural killer cell-based immunotherapy for acute myeloid leukemia

“…CD16 × NKG2D BiKE displayed increased affinity to CD16 and induced superior leukemia cell killing compared to the engineered NKG2D-Fc fusion protein [186]. Besides, CD16 × CLL-1 × IL-15 TriKE displayed robust NK cell activity against AML in vitro and in vivo [187]. These molecules constitute attractive candidates for personalized immunotherapy for AML based on preclinical findings.…”

BiTEs, DARTS, BiKEs and TriKEs—Are Antibody Based Therapies Changing the Future Treatment of AML?

“…The third component is the addition of an IL-15 crosslinker to expand the NK response [ 35 ]. TriKEs with CLEC12A, which is expressed on AML and leukemic stem cells (LSCs), were able to reduce tumor burden in vitro and in mouse models, while successfully sparing HSCs [ 36 ]. In vitro, TriKEs enhanced NK cell cytotoxicity, degranulation, and cytokine release [ 37 ].…”

“…Compared to the CD33 target, the CLEC12A TriKE had fewer off target effects on peripheral blood mononuclear cells (PBMC) with similar efficacy in NK cell activation [ 35 ]. This was further explored in mouse models, demonstrating that the CLEC12A TriKE induced a robust NK cell response, killing AML cells while sparing normal HSCs [ 36 ]. The DART known as CLEC12A-ENG.CD123IL7Ra was synthesized to target CLEC12A with the addition of IL7Ra to the CD123 portion of the DART.…”