Targeting the sodium-dependent multivitamin transporter (SMVT) for improving the oral absorption properties of a retro-inverso Tat nonapeptide

S. Ramanathan, S. Pooyan, S. Stein, P. D. Prasad, J. Wang, Michael J Leibowitz, V. Ganapathy, P. J. Sinko

Research output: Contribution to journalArticle

47 Scopus citations


Purpose. To investigate the potential for delivering large peptides orally by altering their absorptive transport pathways and improving intestinal permeability. The absorptive transport of retro-inverso (R.I.-) K-Tat9 and R.I.-K(biotin)-Tat9, novel peptidic inhibitors of the Tat protein of HIV-1, and their interactions with human SMVT (hSMVT), a high affinity, low capacity transporter, were investigated using Caco-2 and transfected CHO cells. Methods. Following synthesis on a PAL resin using Fmoc chemistry, the transport of R.I.-K-Tat9 (0.01-25 μM) and R.I.-K(biotin)-Tat9 (0.1-25 μM) was evaluated across Caco-2 cells. The transport and kinetics of biotin, biocytin and desthiobiotin (positive controls for SMVT) were also determined. Uptake of R.I.-K-Tat9 and R.I.-K(biotin)-Tat9 (both 0.1-10 μM) was determined in CHO/hSMVT and CHO/pSPORT (control) cells. Results. The absorptive transport of R.I.-K-Tat9 was passive, low (Pm ∼ 1 × 10-6 cm/sec) and not concentration dependent. R.I.-K(biotin)-Tat9 permeability was 3.2-fold higher than R.I.-K-Tat9 demonstrating active (Ea = 9.1 kcal/mole), concentration dependent and saturable transport (Km = 3.3 μM). R.I.-K(biotin)-Tat9 uptake in CHO/hSMVT cells (Km = 1.0 μM) was ∼ 500-fold greater than R.I.-K-Tat9 (at 10 μM). R.I.-K(biotin)-Tat9 transport in Caco-2 and CHO/hSMVT cells was significantly inhibited by known substrates of SMVT including biotin, biocytin, and desthiobiotin. Passive uptake of R.I.-K(biotin)-Tat9 was significantly greater than R.I.-K-Tat9 uptake in CHO/pSPORT cells. Conclusions. These results demonstrate that the structural modification of R.I.-K-Tat9 to R.I.-K(biotin)-Tat9 altered its intestinal transport pathway resulting in a significant improvement in its absorptive permeability by enhancing nonspecific passive and carrier-mediated uptake by means of SMVT. The specific interactions between R.I.-K(biotin)-Tat9 and SMVT suggest that targeting approaches utilizing transporters such as SMVT may substantially improve the oral delivery of large peptides.

Original languageEnglish (US)
Pages (from-to)950-956
Number of pages7
JournalPharmaceutical Research
Issue number7
StatePublished - 2001
Externally publishedYes


  • Biotin
  • Caco-2
  • CHO
  • Oral absorption
  • Tat peptide
  • Vitamin transporter

ASJC Scopus subject areas

  • Chemistry(all)
  • Pharmaceutical Science
  • Pharmacology

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