3003 Background: The KRASG12C mutation is found in approximately 13% of lung adenocarcinomas and 1–3% of other solid tumors, but there is no approved therapy that targets this mutation. AMG 510 is a novel small molecule that specifically and irreversibly inhibits KRASG12C by locking it in an inactive GDP-bound state. Methods: This phase 1, first-in-human, open-label, multicenter study (NCT03600883) is evaluating the safety, tolerability, PK, and efficacy of AMG 510 in adult patients (pts) with locally-advanced or metastatic KRASG12C mutant solid tumors. The primary endpoint is safety; key secondary endpoints include PK, ORR (assessed every 6 weeks [wks]), DOR, and PFS. Key inclusion criteria: KRASG12C mutation identified through DNA sequencing, measurable or evaluable disease, ECOG PS ≤2, life expectancy >3 months (mo). Key exclusion criteria: active brain metastases, myocardial infarction within 6 mo. A dose exploration will determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D). A dose expansion will enroll pts with NSCLC, CRC, and other advanced solid tumors carrying the KRASG12C mutation. AMG 510 will be given PO until disease progression, intolerance, or withdrawal of consent. Results: 22 pts (8 men, 14 women; median age 55.5 y) were enrolled in the first 3 dose cohorts. Tumor types: 6 NSCLC, 15 CRC, 1 other. Most pts (n=17) had ≥3 prior lines of treatment (tx). Median tx duration was 28 d (range: 8–134). 5 pts reported 10 treatment-related AEs (grade 1, n=9; grade 2, n=1); there were no DLTs. Tumor response was evaluated in 9 pts (4 with ≥2 assessments); 13 pts have not reached their first assessment.1 pt had a PR (NSCLC at wks 6 and 12, tx ongoing), 6 pts had SD (4 CRC and 2 NSCLC; median tx duration 9.7 wks [range: 6.3–19.1], tx ongoing), 2 pts had PD. 20 pts are continuing to receive AMG 510. A second PR (NSCLC at wk 6, tx ongoing) was reported after data cutoff. Conclusions: AMG 510 has been well tolerated at the dose levels tested and has shown antitumor activity when administered as monotherapy to patients with advanced KRAS G12C mutant solid tumors. MTD has not been determined, and enrollment into the dose exploration is ongoing. Clinical trial information: NCT03600883.

Purpose Trastuzumab resistance has been linked to activation of the phosphoinositol 3-kinase (PI3K) pathway. Phosphatase and tensin homolog (PTEN) is a dual phosphatase that counteracts the PI3K function; PTEN loss leads to activation of the Akt cascade and the downstream mammalian target of rapamycin (mTOR). Preclinical studies demonstrated that mTOR inhibition sensitized the response to trastuzumab in mice with HER2 overexpressing and PTEN-deficient breast xenografts. Our trial evaluated the safety and efficacy of the combination of everolimus and trastuzumab in women with HER2-overexpressing metastatic breast cancer (MBC) that progressed on trastuzumab-based therapy. Patients and Methods This represents a pooled analysis (n = 47), stemming from two trials that occurred concurrently in The University of Texas MD Anderson Cancer Center, Beth Israel Deaconess Medical Center, and Dana-Farber Cancer Institute. Patients with HER2-overexpressing MBC who had progressed on trastuzumab-based therapy received trastuzumab every 3 weeks in combination with daily everolimus. Results Among 47 patients, the combination of everolimus and trastuzumab provided partial responses in seven patients (15%) and persistent stable disease (lasting 6 months or longer) in nine patients (19%), resulting in a clinical benefit rate of 34%. The median progression-free survival (PFS) was 4.1 month. Fatigue, infection, and mucositis were the predominant nonhematologic toxicities. Trastuzumab did not have significant influence on the pharmacokinetic profile of everolimus. Patients with PTEN loss demonstrated decreased overall survival (P = .048). However, PFS was not affected by PTEN loss. Conclusion Inhibition of mTOR results in clinical benefit and disease response in patients with trastuzumab-resistant HER2-overexpressing MBC.

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In this large evaluation of RDI in US clinical practice, physicians frequently administered myelosuppressive agents at dose intensities lower than those of standard regimens.

ABSTRACT

Biosimilars of biologics used for cancer treatment and supportive care are expected to enter the U.S. market soon. Biosimilars will be highly similar to their reference products, but unlike generic drugs, not identical. Differences between a biosimilar and its reference product may arise because of the complexity of biologics, and differences in the cell lines and processes used during manufacturing. Biosimilars will be approved in the United States through a regulatory pathway based on comparative analytical and clinical studies for their characterization and demonstration of no clinically meaningful differences from their reference products. Unlike generics, initial approval may not include interchangeability, as additional evidence may be required before a biosimilar could be approved as interchangeable with its reference product; interchangeable designation could allow pharmacy-level substitution without prescriber intervention. In some cases, the U.S. Food and Drug Administration (FDA) may extrapolate an indication that has not been formally investigated for the biosimilar but that is approved for the reference product. Robust safety monitoring of all biologics is important to track and accurately attribute adverse events, particularly because their inherent complexity and manufacturing differences make them susceptible to structural changes that can affect safety (e.g., immunogenicity). Accuracy of postapproval safety reports will partly depend on the biosimilar naming approach. Potential cost savings should be evaluated in the context of differences in manufacturers' patient-assistance programs, copayments, and institutional costs. A manufacturer's ability to ensure reliable supply of high-quality biosimilars should also be considered. Broad understanding of these issues is critical for oncologists preparing for their use in clinical practice.

Dose delays, dose reductions, and reduced RDI were common. In advanced breast cancer, health status and triple-negative disease were significantly associated with mortality. In advanced ovarian cancer, dose reductions and tumor histology were significantly associated with mortality. These results can help identify potential risk factors and characterize the effect of chemotherapy dose modification strategies on mortality.