Recombinant anti-CD25 immunotoxin RFT5(SCFV)-ETA' demonstrates successful elimination of disseminated human Hodgkin lymphoma in SCID mice.
Since clinical phase-I/II trials in patients with resistant Hodgkin's lymphoma treated with the chemically linked anti-CD25 ricin-A-chain immunotoxin RFT5-SMPT-dgA indicate promising results for patients with minimal residual disease, we constructed a new immunotoxin by fusing the RFT5 single-chain variable fragment to a deletion mutant of Pseudomonas exotoxin A (ETA'). The recombinant protein was directed into the periplasmic space of E. coli by means of the pET-derived expression vector pBM1.1 and our newly developed expression/purification method. Biologically active RFT5(scFv)-ETA' was isolated by freezing/thawing and purified by immobilized metal-ion affinity and molecular-size-chromatography. RFT5(scFv)-ETA' was subsequently used for the treatment of disseminated human Hodgkin's lymphoma in a SCID-mouse model. The mean survival time (MST) of L540rec-challenged SCID mice was 38.1 days. A single i.v. injection of 40 microg recombinant immunotoxin (rIT) 1 day after tumor inoculation resulted in 100% tumor-free mice, extending the MST to more than 220 days (p < 0.0001). The blood-distribution time T(1/2)alpha was 39.65 min, the serum elimination time T(1/2)alpha, 756.6 min. All animals were assessed for soluble interleukin-2 receptor alpha, which is directly correlated to tumor burden. Soluble CD25 was not detectable in mice treated with the rIT. Our findings, concerning potent anti-tumor effects of a recombinant anti-CD25 immunotoxin against disseminated Hodgkin's lymphoma in SCID mice reported here demonstrate that RFT5(scFv)-ETA' might be suitable for further evaluation against Hodgkin's lymphoma in humans.
Barth
S
S
Department I of Internal Medicine, University of Cologne, Cologne, Germany.
Huhn
M
M
Matthey
B
B
Schnell
R
R
Tawadros
S
S
Schinköthe
T
T
Lorenzen
J
J
Diehl
V
V
Engert
A
A
D000818:Animals; D000911:Antibodies, Monoclonal / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004195:Disease Models, Animal; D006689:Hodgkin Disease / Q000188:drug therapy* / Q000401:mortality / Q000517:prevention & control; D006801:Humans; D000922:Immunotoxins / Q000627:therapeutic use*; D051379:Mice; D016513:Mice, SCID; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D011994:Recombinant Proteins / Q000627:therapeutic use; D057127:Single-Chain Antibodies
D000911:Antibodies, Monoclonal; D000922:Immunotoxins; C117703:RFT5(scFv)-ETA'; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D057127:Single-Chain Antibodies