Novel flt3 antibodies and antibody-drug-conjugates based thereon, therapeutic methods and uses thereof in combination with tyrosine kinase inhibitors

An anti-FLT3 antibody (Receptor-type tyrosine-protein kinase FLT3), wherein said anti-FLT3 antibody is capable of the following:

• a) binding to an extracellular domain of said FLT3;
• b) cross-reactivity with cynomolgus monkey (e.g., Macaca fascicularis) FLT3 (e.g., having UniProtKB Accession Number:
• Q95M30);
• c) internalization, preferably by the means of the antigen-mediated antibody internalization;
• d) binding to an extracellular epitope of said FLT3, wherein said extracellular epitope comprising one or more of the following sequences:
• i) SEQ ID NO:
• 2 (Epitope 1), preferably further comprising SEQ ID NO:
• 4 (Epitope 3);
• and/or
• ii) SEQ ID NO:
• 3 (Epitope 2), preferably further comprising SEQ ID NO:
• 4 (Epitope 3);
• e) preferably said FLT3 is a human FLT3 having SEQ ID NO:
• 1 or UniProtKB Accession Number:
• P36888, further preferably said extracellular domain ranges from amino acids 27 to 543 of SEQ ID NO:
• 1.