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Rigshospitalet - a part of Copenhagen University Hospital
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Phase 1 study of the immunotoxin LMB-100 in patients with mesothelioma and other solid tumors expressing mesothelin

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  • Raffit Hassan
  • Christine Alewine
  • Idrees Mian
  • Anna Spreafico
  • Lillian L Siu
  • Carlos Gomez-Roca
  • Jean-Pierre Delord
  • Antoine Italiano
  • Ulrik Lassen
  • Jean-Charles Soria
  • Rastilav Bahleda
  • Anish Thomas
  • Seth M Steinberg
  • Cody J Peer
  • William D Figg
  • Gerhard Niederfellner
  • Valérie Méresse Naegelen
  • Ira Pastan
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BACKGROUND: LMB-100 is an antibody-toxin conjugate with an antimesothelin Fab linked to a 24-kilodalton portion of Pseudomonas exotoxin A with mutations that decrease immunogenicity. The objective of the current first-in-human phase 1 study was to determine the maximum tolerated dose (MTD) and safety in patients with advanced solid tumors expressing mesothelin.

METHODS: Cohorts of 1 to 7 patients received intravenous LMB-100 at 7 dose levels from 40 µg/kg to 250 µg/kg intravenously on days 1, 3, and 5 of a 21-day cycle.

RESULTS: Of the 25 patients accrued, 17 had mesothelioma, 3 each had ovarian or pancreatic cancer, and 2 patients had gastric cancer. Dose-limiting toxicities occurred in 2 of 4 patients treated at a dose of 250 µg/kg (capillary leak syndrome) and in 3 of 7 patients treated at a dose of 170 µg/kg (creatinine increase). The MTD of LMB-100 was 140 µg/kg. Of the 10 patients with mesothelioma who were treated at doses of 170 µg/kg or 140 µg/kg, 8 had stable disease and 2 developed progressive disease. Peak LMB-100 plasma concentrations were dose-dependent during cycle 1. The development of antidrug antibodies decreased LMB-100 blood levels in 8 of 21 patients (38%) who received cycle 2 and 9 of 11 patients (81.8%) who received cycle 3.

CONCLUSIONS: The MTD for single-agent LMB-100 was found to be 140 µg/kg given on a schedule of every other day for 3 doses every 3 weeks. Although less immunogenic than the first-generation antimesothelin immunotoxin SS1P, the majority of patients developed antidrug antibodies after 2 cycles, indicating that LMB-100 has limited antitumor efficacy as a single agent. Phase 2 studies of LMB-100 plus pembrolizumab currently are ongoing for patients with mesothelioma and lung cancer.

LAY SUMMARY: Mesothelin, a cell surface antigen, is an attractive target for cancer therapy given its limited expression in normal human tissues and high expression in many human cancers. LMB-100 is a recombinant antimesothelin immunotoxin consisting of a humanized antimesothelin antibody fragment fused to a truncated Pseudomonas exotoxin A. In the current study, the authors determined the safety, maximum tolerated dose, and pharmacokinetics of LMB-100, as well as the generation of antidrug antibodies. Ongoing phase 2 clinical trials are evaluating the combination of LMB-100 plus pembrolizumab in patients with treatment-refractory mesothelioma and non-small cell lung cancer.

Original languageEnglish
JournalCancer
Volume126
Issue number22
Pages (from-to)4936-4947
Number of pages12
ISSN0008-543X
DOIs
Publication statusPublished - 15 Nov 2020

ID: 61507086