Citations

Abstract Background Repotrectinib, a next-generation ROS1/TRK tyrosine kinase inhibitor, is approved for ROS1 fusion-positive non-small cell lung cancer and NTRK fusion-positive solid tumors. Its side effects and safety management strategies require further characterization. Patients and Methods The safety profile of repotrectinib (treatment-emergent/related adverse events [TEAEs/TRAEs]) was established in patients who initiated treatment at the recommended dose (160 mg daily [QD] for 14 days, then 160 mg twice daily [BID]) across all cohorts of the global, multicenter phase 1/2 TRIDENT-1 study. AE management strategies were outlined. Results In 472 patients, the most common TRAEs (dizziness [58%] and dysgeusia [50%]) were likely TRK inhibition-related. Median relative dose intensity was 90%; 14% (n = 66/472) of patients did not increase their initial QD dose to BID (mostly due to CNS AEs). Rates of dizziness (median onset, 7 days) were similar in patients with/without baseline brain metastases. Dose modifications downgraded severity or resolved dizziness in 78% of patients; 58% of patients had pharmacologic intervention without dose modification. Dizziness was downgraded/resolved in 62% (n = 120/195) of patients who did not receive dose modification or pharmacologic intervention. Treatment-related cognitive impairment and weight gain occurred in 19% and 12% of patients, respectively. Treatment-emergent withdrawal pain occurred in 14% of patients (median resolution time, 2.1 weeks). Dose interruption and reduction from TRAEs occurred in 39% and 38% of patients, respectively; 10% reported later re-escalation back to 160 mg BID. Conclusion Many repotrectinib AEs, including neurological AEs secondary to TRK inhibition, were mitigated with appropriate management, including dose modification and/or pharmacologic intervention.

Abstract Purpose: Rearranged during transfection (RET) alterations are oncogenic drivers across solid tumors. Selective RET inhibitors (SRI) selpercatinib and pralsetinib have transformed outcomes for patients with RET-altered malignancies. Limited knowledge exists on genomic mechanisms of resistance to SRI. Experimental Design: We established “RETgistry,” a global consortium of patients with advanced RET-altered solid tumors who received SRI and underwent postprogression tissue or plasma biopsies assessed by next-generation sequencing. Frequencies of secondary RET resistance mutations and acquired non-RET gene alterations were determined. Progression-free survival (PFS) and time to treatment discontinuation (TTD) on first SRI were estimated with the Kaplan–Meier method. Results: RETgistry included 109 patients with RET-altered advanced solid tumors (lung, n = 94; thyroid, n = 15) who underwent 143 post-SRI progression biopsies (tissue, 91; plasma, 52). The median PFS and TTD were 13.9 months [95% confidence interval (CI), 10.1–16.6] and 17.3 months (95% CI, 14–20.2), respectively. Secondary RET mutations were detected in 20 (14%) biopsies [lung cancer, 15 (12.4%) and thyroid carcinoma, 5 (22.7%)]. Common acquired off-target alterations involved MET (18.2%; amplification, 15%), TP53 (8.2%), APC (7.6%), KRAS (7.1%), KEAP1 (5.9%), and CDKN2A/B (5.3%). MET alterations were enriched in post-SRI versus pre-SRI specimens (full cohort, 17.6% vs. 2.0%, P = 0.022; lung cancer, 19.1% vs. 2.1%, P = 0.022). Conclusions: The prevalence of secondary RET mutations after SRI was low, underscoring a greater role for off-target resistance. Recurrent acquired alterations involving tumor suppressor genes or upstream regulators of MAPK and PI3K pathways were identified, most commonly MET amplification. Continued efforts to characterize SRI resistance biology are critical to guide the development of novel therapeutic strategies.

9065 Background: Rearranged during transfection ( RET) gene alterations are the oncogenic driver in diverse tumor types, including RET fusions identified in 1-2% of non-small cell lung cancers (NSCLC). While RET-selective tyrosine kinase inhibitors (TKIs) selpercatinib and pralsetinib are effective, acquired drug resistance remains a challenge. Here, we report the initial results from the RETgistry, an international consortium aimed at elucidating mechanisms of resistance to RET TKIs across RET-altered solid tumors. Methods: This was a retrospective analysis performed across 16 institutions. Patients (pts) were eligible if they had advanced solid tumor harboring an oncogenic RET alteration, received ≥1 RET TKI with disease progression, and underwent resistant tumor or liquid biopsy for next-generation sequencing (NGS). Results: A total of 103 time-distinct biopsies (62 tissue, 30 plasma, 11 paired tissue/plasma) were included in analysis, obtained from 88 pts with progression on a RET-selective TKI [selpercatinib (n = 70), pralsetinib (n = 14), selpercatinib and pralsetinib sequentially (n = 4)]. Pts had the following tumor types: 72 NSCLC (69% KIF5B-RET, 21% CCDC6-RET, 10% other RET fusion), 13 medullary thyroid cancer (TC) (54% RET M918T, 46% other RET mutation), and 2 papillary and 1 anaplastic TC (all, RET fusion). Median age was 58 (range, 21-86); 48% were male with 89% never/light smokers. Median duration of RET TKI preceding biopsies [first-line, n = 32 (31%); second-line, n = 42 (41%); third-/greater-line, n = 29 (28%)] was 16.5 months (mos) (95% CI, 14.0-19.6); median PFS was 14.1 mos (95% CI, 9.3-17.0). Resistant biopsies were obtained at median 15.0 mos from TKI initiation (range, 1.8-58.8). Acquired RET mutations were detected in 14 (14%), most common being G810 substitutions in 12 (12%). Potential off-target resistance gene alterations identified in 43 cases (42%) included MET amplification (14%), BRAF V600E or fusion (2%), KRAS gain or mutation (5%), ERBB2 amplification (2%), EGFR amplification (3%), ROS1 fusion (1%), and activating PIK3CA mutation or PTEN loss (4%). No resistant lung cancer biopsy demonstrated small cell transformation. The duration of TKI therapy (HR 0.64, p = 0.11) or PFS (HR 0.75, p = 0.33) did not differ according to the presence of on-target vs off-target resistance. NGS analyses of pre-RET-selective TKI tumors (n = 92) revealed frequent co-occurring alterations in TP53 (29%) and CDKN2A/B (12%). Conclusions: On-target resistance to RET inhibition due to acquired RET mutations was less common than off-target resistance, identified in 14%. The majority of RET TKI resistance is mediated by off-target mechanisms such as bypass receptor tyrosine kinase activation. Further studies are warranted to enable the development of therapeutic strategies to address resistance in pts with RET-altered tumors. The RETgistry accrual and data analyses continue.

3594 Background: Selpercatinib (LOXO-292) is a highly selective and potent small molecule RET kinase inhibitor. Here we report an update on the efficacy and safety of selpercatinib in RET-mutant medullary thyroid cancer (MTC). Methods: Patients with RET-mutant MTC were enrolled to the Phase 1/2 LIBRETTO-001 trial (NCT03157128), a global, multicenter trial (16 countries, 89 sites). Following the Phase 1 dose escalation portion of the trial, patients received the recommended dose of 160 mg orally twice daily. Each cycle was 28 days. The primary endpoint was objective response rate (ORR) per RECIST 1.1. Secondary endpoints included duration of response (DoR) and safety. Per health authority agreement, the primary analysis set was defined as the first 55 consecutively enrolled patients previously treated with multikinase inhibitors cabozantinib and/or vandetanib. Patients naïve to cabozantinib and vandetanib treatment were analyzed separately. All analyses were based on a 16-Dec-2019 data cutoff date. Results: In the primary analysis set of prior cabozantinib and/or vandetanib-treated patients with MTC (n = 55), the ORR by investigator assessment was 62% (95% CI 47.7–74.6, n = 34/55) and the median DoR was not reached (95% CI 18.4 months–not estimable) despite a median follow-up of 14.8 months. In cabozantinib/vandetanib treatment-naïve patients (n = 88), the ORR by investigator assessment was 69% (95% CI 58.6–78.7, n = 61/88, including 2 responses pending confirmation). Of the 59 confirmed responding patients, with a median follow-up of 8 months, responses were ongoing for 57 responders at the time of the analysis. In the safety analysis set consisting of all selpercatinib dosed patients (N = 702), the most common treatment-related adverse events (TRAEs) that occurred in ≥15% of patients were dry mouth (33.3%), increased AST (24.5%), increased ALT (23.8%), hypertension (23.2%), diarrhea (19.7%), and fatigue (16.8%). Only 2% (14 of 702) of patients discontinued selpercatinib for TRAEs. Conclusions: Selpercatinib use was associated with marked and durable antitumor activity in prior cabozantinib and/or vandetanib-treated patients and in cabozantinib/vandetanib-naïve patients with RET-mutant MTC, with the majority of responses ongoing in both cohorts. Selpercatinib was well tolerated. Efficacy data assessed by independent review committee based on the 16-Dec-2019 data cutoff date will be presented. Clinical trial information: NCT03157128 .

6571 Background: Chronic lymphocytic leukemia (CLL) is associated with an increased risk of developing second cancers. However, it is unknown whether CLL alters the natural history of these cancers once they occur. Methods: All patients with breast (n=583,838), colon (n=412,932), prostate (n=632,922), lung (n=489,290), kidney (n=95,902), pancreas (n=82,121) and ovarian (n=61,958) cancer reported to the Surveillance, Epidemiology, and End Results (SEER) Program from 1990 to 2007 were identified. Overall survival (OS; death due to any cause) and cancer-specific survival (death due to cancer site of interest) were examined, comparing patients with or without pre-existing CLL. Age- and sex-adjusted hazard ratios (HRs) were calculated. Results: OS for patients with pre-existing CLL was inferior for patients with breast (HR=1.61; p<0.001), colon (HR=1.65; p<0.001), kidney (HR=1.41; p<0.001), prostate (HR=1.75; p<0.001), and lung (HR=1.22; p<0.001) cancer after adjusting for age and sex. After excluding CLL-related deaths, OS remained shorter among patients with breast (p<0.001), colon (p<0.001), kidney (p=0.03), prostate (p<0.001), and lung (p<0.001) cancer. Cancer-specific survival was inferior for patients with breast (HR=1.29; p=0.03), colon (HR=1.75; p<0.001), and lung cancer (HR=1.17; p<0.001) who had pre-existing CLL after adjusting for age and sex. Conclusions: Several common cancers, including breast, colon, and lung, have inferior overall and cancer-specific survival when there is coexistent CLL. [Table: see text]

Two lysine acyltransferases govern histone H3 propionylation at lysine 23 in normal and pathological conditions.

Abstract Abstract 2893 Introduction: Monoclonal B-Cell Lymphocytosis (MBL) is a common asymptomatic condition characterized by a clonal B-cell population detected in the blood or bone marrow. The prevalence of MBL is approximately 3–5% in adults over age 40 but rises with age. MBL is a precursor state to CLL and other types of indolent non-Hodgkin lymphoma (NHL). Only a small subset of patients with MBL comes to clinical attention, typically during evaluation for low grade lymphocytosis (designated now as clinical MBL). The rate of progression to CLL requiring treatment among individuals with clinical MBL is ∼1%/yr, and the vast majority of patients with MBL will never develop a B-cell malignancy. Recent data indicate that individuals with MBL are at increased risk of infection similar to CLL. It is unknown whether individuals with MBL are at risk for other adverse outcomes associated with CLL, such as increased risk of non-hematologic cancers (NHC). We investigated the incidence of NHC among patients with clinical MBL and compared this to a cohort of general medicine patients and a cohort of CLL patients. Methods: Mayo Clinic Rochester (MCR) is the primary center for hematologic care in a region including southeastern Minnesota, northern Iowa, and western Wisconsin. No other hematology specialty centers are available within a 50 mile radius of MCR. To explore the risk of NHC in a local, community dwelling cohort of individuals with clinically-identified, CLL-phenotype MBL, we used the MCR CLL database to identify all individuals with newly diagnosed MBL seen in the MCR Hematology Division between January 1, 1999 and December 31, 2009. Analysis was limited to 154 MBL cases residing within 50 miles of MCR. The comparison cohort consisted of 596 adult general medicine patients, with no prior cancer, residing within 50 miles of MCR, who were seen for a general medical exam and enrolled as controls in a case-control study for NHL between April 25, 2004 and December 31, 2009. Rates of NHC in the MBL cohort were also compared to a cohort of 174 patients with newly diagnosed CLL seen in the same time interval as the MBL cohort and also living within 50 miles of MCR. NHC were identified using the Mayo Clinic Cancer Tumor Registry as well as review of medical records in all 3 cohorts. Patients with a NHC diagnosis >3 months prior to the diagnosis date of MBL/CLL were excluded from analysis while those with MBL/CLL and a NHC within 3 months of one another were considered to have a concurrent diagnosis. Results: There were 125 patients in the MBL cohort, 153 in the CLL cohort, and 596 in the control cohort after excluding patients with prior cancers. The MBL and CLL patients tended to be older (median age MBL=69, CLL=68, Control=58; p<0.0001) and more likely to be male (% male MBL=61, CLL=67, Control=46; p<0.0001) than the controls. After a median follow-up of 4.2 years (range 0–11), 20 (16%) individuals with MBL developed NHC as compared to 22 (4%) of the controls (Hazard Ratio (HR) MBL relative to control=5.0; 95% confidence interval (CI)=(2.6, 9.4; p<0.0001). Twenty CLL patients (13%) developed NHC, supporting a similar rate to that of MBL patients (HR MBL relative to CLL=1.3; 95% CI=(0.6, 2.5; p=0.49;See Figure). Specifically, the MBL cohort had a higher incidence of cancer of the breast, lung, and nervous system than that of the control cohort. The higher risk of NHC among individuals with CLL and MBL persisted even when patients with “concurrent diagnosis” of CLL/MBL and NHC were excluded (p=0.006) and when patients treated for progressive CLL were censored at the date of treatment (p=0.001) Finally, we performed a pooled multivariable analysis of all patients (n=874) adjusting for age, sex, major co-morbidities, presence of MBL, and diagnosis of CLL. Age (HR each year older=1.03; 95% CI 1.01–1.06; p=0.003), major comorbidities (HR=1.81; 95% CI 1.07–3.00; p=0.02), CLL (HR=2.10; 95% CI 1.01–4.01; p=0.04), and MBL (2.47; 95% CI 1.30–4.69; p=0.02) were independent risk factors for NHC. The results were similar when the effects of age was modeled in a non-linear (e.g. logarithmic) manner. Conclusions: In this cohort study, patients with newly diagnosed clinical MBL had a 2.5-fold increased risk of developing NHC relative to the control cohort. MBL was an independent risk factor for development of NHC after adjusting for age, sex, and other comorbidities. This finding adds to the growing evidence that clinical MBL has a distinct clinical phenotype. Disclosures: Shanafelt: Genentech: Research Funding; Glaxo-Smith-Kline: Research Funding; Cephalon: Research Funding; Hospira: Research Funding; Celgene: Research Funding; Polyphenon E International: Research Funding.

Assessment of tumor-infiltrating lymphocytes (TILs) in histopathologic specimens can provide important prognostic information in diverse solid tumor types, and may also be of value in predicting response to treatments. However, implementation as a routine clinical biomarker has not yet been achieved. As successful use of immune checkpoint inhibitors and other forms of immunotherapy become a clinical reality, the need for widely applicable, accessible, and reliable immunooncology biomarkers is clear. In part 1 of this review we briefly discuss the host immune response to tumors and different approaches to TIL assessment. We propose a standardized methodology to assess TILs in solid tumors on hematoxylin and eosin sections, in both primary and metastatic settings, based on the International Immuno-Oncology Biomarker Working Group guidelines for TIL assessment in invasive breast carcinoma. A review of the literature regarding the value of TIL assessment in different solid tumor types follows in part 2. The method we propose is reproducible, affordable, easily applied, and has demonstrated prognostic and predictive significance in invasive breast carcinoma. This standardized methodology may be used as a reference against which other methods are compared, and should be evaluated for clinical validity and utility. Standardization of TIL assessment will help to improve consistency and reproducibility in this field, enrich both the quality and quantity of comparable evidence, and help to thoroughly evaluate the utility of TILs assessment in this era of immunotherapy.