Modulators of tight junction permeability
The invention relates to compounds capable of modulating the permeability of junctions between epithelial cells, and their use to facilitate delivery of substances such as therapeutic and diagnostic agents across epithelial surfaces. In particular the invention relates to the identification of key amino acids in the known permeation enhancer PIP250 and the provision of new permeation enhancing peptides with more transient activity, thus providing faster epithelial recovery.
1 . An agent capable of increasing epithelial permeability, wherein the agent comprises a peptide of no more than 15 amino acids in length, said peptide comprising a core sequence of Formula I:
x3-k-x5-k (Formula I)
wherein
(i) x3 is D-Phe and
x5 is selected from D-Ala, D-Leu and Gly; or
(ii) x3 is D-Ala and x5 is selected from D-Val, D-Ala, D-Leu and Gly.
2 . The agent according to claim 1 , wherein the peptide has a core sequence of Formula II:
x3-k-x5-ktk (Formula II)
wherein
(i) x3 is D-Phe and x5 is selected from D-Ala, D-Leu and Gly; or
(ii) x3 is D-Ala and x5 is selected from D-Val, D-Ala, D-Leu and Gly.
3 . The agent according to claim 1 , wherein the agent is capable of crossing the plasma membrane of an epithelial cell.
4 . The agent according to claim 3 , wherein the peptide comprises one or more additional sequence(s) capable of mediating transit across the plasma membrane.
5 . The agent according to claim 4 , wherein the peptide comprises the residues rr N-terminal of the core sequence, and/or krk C-terminal of the core sequence.
6 . The agent according to claim 1 , wherein the peptide comprises or consists of the sequence:
rr-x3-k-x5-ktkkrk wherein (i) x3 is D-Phe and x5 is selected from D-Ala, D-Leu and Gly; or
(ii) x3 is D-Ala and x5 is selected from D-Val, D-Ala, D-Leu and Gly.
7 . The agent according to claim 1 , wherein the core sequence of Formula I is selected from the group consisting of akvk, fkak and akak.
8 . The agent according to claim 2 , wherein the core sequence of Formula II is selected from the group consisting of akvktk, fkaktk and akaktk.
9 . The agent according to claim 1 , wherein the peptide comprises or consists of the sequence:
rrakvktkkrk
or
rrfkaktkkrk.
10 . The agent according to claim 1 , having the formula
R 1 —Z—R 2 wherein:
R 1 is H, C 1-4 alkyl, acetyl, formyl, benzoyl or trifluoroacetyl;
R 2 is OH or NH 2 ;
and Z represents a peptide sequence as described in claim 1 .
11 . The agent according to claim 10 , which is:
H-rrakvktkkrk-NH 2
or
H-rrfkaktkkrk-NH 2 .
12 . A pharmaceutical composition comprising the agent according to claim 1 and a pharmaceutically acceptable carrier.
13 . The pharmaceutical composition of claim 12 further comprising a substance to be delivered across an epithelial surface.
14 . The pharmaceutical composition according to claim 13 , wherein the substance is a diagnostic or therapeutic agent.
15 . A kit comprising:
(i) a first composition comprising an agent according to claim 1 ; and
(ii) a second composition comprising a substance to be delivered across an epithelial surface.
16 . A kit according to claim 15 , wherein the substance to be delivered is a diagnostic or therapeutic agent.
17 . A method of increasing permeability of an epithelial surface comprising the step of administering the agent according to claim 1 to an epithelial surface.
18 . A method of delivering a substance across an epithelial surface comprising the step of administering (a) the agent according to claim 1 and (b) a substance to be delivered across an epithelial surface to an epithelial surface.
19 . The method according to claim 18 , wherein the substance is a diagnostic or therapeutic agent.