Table 1.

Putative CD44 binders		References and comments
Natural Ligand
HA8 : [GlcNAc-GlcUA]4	[21] [4a] [4b] [20]	Kd = 24.6 μM by ITCa
Antibodies
DF1485	[25]	From Santa Cruz Biotechnolgy Kd ≪ 400 nM by NMRb
Roche		Patent Number: WO 2011095498 A1c
Peptides
A6 Peptide: Ac-KPSSPPEE-NH2	[25] [9]	In phase 2 for CLL		No direct bind to recombinant hCD44(21–178) by NMRd
A5G27: H-RLVSYNGIIFFLK-NH2	[26]	Laminin α5 peptide
Ac-SRPQGPFL-NH2	[28]	From blade I of MMP-9
Fragment
Compound 3:	[16]	Reported Kd by SPR is 0.9 mM No appreciable binding by NMR or ITCe

^aIsothermal Titration Calorimetry (ITC) data as reported in Figure 1. The data are in agreement with similar measurements from ref. ^[17].

^bNo K_d was reported in literature for this antibody. By NMR spectroscopy with recombinant ¹⁵N-hCD44(21–178) we estimated a K_d value ≪ 400 nM.

^cThis antibody is not commercially available. We tested peptides regions cited in the patent as putative CD44 binding elements. However, under the reported experimental condition, none of these peptides bound to hCD44(21–178) significantly.

^dUsing ¹⁵N-hCD44(21–178) at 20 μM we could not detect significant binding for these peptides when tested at a concentration up to 500 μM.

^eIn [¹H,¹⁵N]-sofast-HMQC correlation spectra with ¹⁵N-hCD44(21–178) at 20 μM, compound 3 did not show appreciable binding up to 20 mM. In addition, the compound was not able to significantly displace the binding of HA₈ to CD44 at 55 mM by ITC (see text and supporting information).