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Cancer Res. 2014 Oct 15;74(20):5700-10. doi: 10.1158/0008-5472.CAN-14-1141. Epub 2014 Aug 21.

Development of novel ADCs: conjugation of tubulysin analogues to trastuzumab monitored by dual radiolabeling.

Author information

1
Department of Otolaryngology/Head and Neck Surgery, VU University Medical Center, Amsterdam, the Netherlands.
2
Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, the Netherlands.
3
KemoTech s.r.l., Parco Scientifico della Sardegna, Edificio 3, Pula, Cagliari, Italy.
4
Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel.
5
KemoTech s.r.l., Parco Scientifico della Sardegna, Edificio 3, Pula, Cagliari, Italy. Dipartimento C.M.I.C. del Politecnico di Milano and C.N.R.-I.C.R.M., Milano, Italy.
6
Dipartimento C.M.I.C. del Politecnico di Milano and C.N.R.-I.C.R.M., Milano, Italy. Kosterlitz Centre for Therapeutics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, United Kingdom.
7
Department of Otolaryngology/Head and Neck Surgery, VU University Medical Center, Amsterdam, the Netherlands. Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, the Netherlands. gams.vandongen@vumc.nl.

Abstract

Tubulysins are highly toxic tubulin-targeting agents with a narrow therapeutic window that are interesting for application in antibody-drug conjugates (ADC). For full control over drug-antibody ratio (DAR) and the effect thereof on pharmacokinetics and tumor targeting, a dual-labeling approach was developed, wherein the drug, tubulysin variants, and the antibody, the anti-HER2 monoclonal antibody (mAb) trastuzumab, are radiolabeled. (131)I-radioiodination of two synthetic tubulysin A analogues, the less potent TUB-OH (IC50 > 100 nmol/L) and the potent TUB-OMOM (IC50, ~1 nmol/L), and their direct covalent conjugation to (89)Zr-trastuzumab were established. Radioiodination of tubulysins was 92% to 98% efficient and conversion to N-hydroxysuccinimide (NHS) esters more than 99%; esters were isolated in an overall yield of 68% ± 5% with radiochemical purity of more than 99.5%. Conjugation of (131)I-tubulysin-NHS esters to (89)Zr-trastuzumab was 45% to 55% efficient, resulting in ADCs with 96% to 98% radiochemical purity after size-exclusion chromatography. ADCs were evaluated for their tumor-targeting potential and antitumor effects in nude mice with tumors that were sensitive or resistant to trastuzumab, using ado-trastuzumab emtansine as a reference. ADCs appeared stable in vivo. An average DAR of 2 and 4 conferred pharmacokinetics and tumor-targeting behavior similar to parental trastuzumab. Efficacy studies using single-dose TUB-OMOM-trastuzumab (DAR 4) showed dose-dependent antitumor effects, including complete tumor eradications in trastuzumab-sensitive tumors in vivo. TUB-OMOM-trastuzumab (60 mg/kg) displayed efficacy similar to ado-trastuzumab emtansine (15 mg/kg) yet more effective than trastuzumab. Our findings illustrate the potential of synthetic tubulysins in ADCs for cancer treatment.

PMID:
25145670
DOI:
10.1158/0008-5472.CAN-14-1141
[Indexed for MEDLINE]
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