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D.K. Strickland

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    ORAL 10 - SCLC (ID 98)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Small Cell Lung Cancer
    • Presentations: 1
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      ORAL10.01 - A DLL3-Targeted ADC, Rovalpituzumab Tesirine, Demonstrates Substantial Activity in a Phase I Study in Relapsed and Refractory SCLC (ID 1598)

      10:45 - 12:15  |  Author(s): D.K. Strickland

      • Abstract
      • Slides

      Rovalpituzumab tesirine (i.e. SC16LD6.5) is a Delta-like protein 3 (DLL3) targeted antibody-drug conjugate (ADC) comprised of a humanized monoclonal antibody, dipeptide linker, and pyrrolobenzodiazepine (PBD) dimer toxin with a drug-to-antibody ratio of 2. DLL3 is highly expressed in human neuroendocrine tumors and their tumor-initiating cells, including approximately two-thirds of small cell lung cancer (SCLC). DLL3 is not expressed at detectable levels in normal tissues. Rovalpituzumab tesirine induced tumor regression and prolonged time to progression significantly outperforming cisplatin/etoposide in DLL3-expressing SCLC patient-derived xenograft tumor models. Based on this promising activity, a first-in-human phase I trial in patients (pts) with recurrent SCLC was initiated and preliminary results are reported below.

      SCLC pts with progressive disease after 1 or 2 previous lines of therapy received escalating doses of rovalpituzumab tesirine as a single agent once every 3 weeks (Q3W) in 1-3 pt cohorts until dose limiting toxicities (DLTs) were observed. The doses were 0.05, 0.1, 0.2, 0.4 and 0.8 mg/kg Q3W. Midway through accrual, pharmacokinetic data revealed a longer than expected ADC half-life of ~11 days, prompting evaluation of a Q6W schedule. A DLL3 antibody was developed and utilized to assess antigen expression in archived tumor specimens. Biomarker positive (BM+) tumors were defined by IHC membrane-associated H-Scores ≥ 120.

      52 pts were treated: 34 Q3W and 18 Q6W; 24F/28M; median age, 61 years (44-82). Acute and chronic DLTs of thrombocytopenia and capillary leak syndrome (CLS) were observed at 0.8 and 0.4 mg/kg Q3W, respectively. Maximum tolerated doses (MTD) of 0.2 mg/kg Q3Wx3 cycles and 0.3 mg/kg Q6Wx2 cycles were further evaluated in expansion cohorts. The most common treatment emergent adverse events of any grade among all pts were fatigue (40%), rash (39%), nausea (29%), dyspnea (23%), decreased appetite (21%) and vomiting (21%). Grade 3+ CLS and thrombocytopenia were seen in 7 (14%) and 3 (6%) pts, respectively, with no reported Grade 5 toxicity. Of 38 archived tumor specimens received from enrolled pts, 23 (61%) were DLL3 BM+. Among the 16 confirmed DLL3 BM+ pts treated at the MTDs, 7 pts (44%) had partial response (PR) and 8 pts (50%) achieved stable disease (SD) for a combined clinical benefit rate (CBR) of 94%. In all evaluable pts treated at the MTD without regard for DLL3 biomarker status (n=32), the ORR was 22% (n=7 PR) and SD 53% (n=17), for a CBR of 75%. Notably, all pts with PRs that were treated at the MTD, and those having the most durable clinical benefit (up to 569 days OS), were BM+. Similar response rates were observed among pts sensitive and refractory to first-line therapy, and in the third-line setting where no standard-of-care currently exists.

      Rovalpituzumab tesirine, a first-in-class DLL3-targeted ADC, has manageable toxicity and demonstrated significant anti-tumor activity (44% ORR and 95% CBR) as a single agent in second- and third-line pts with recurrent DLL3 BM+ SCLC. A pivotal study is being planned.

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