LTK mutations responsible for resistance to lorlatinib in non-small cell lung cancer harboring CLIP1-LTK fusion.

The CLIP1-LTK fusion was recently discovered as a novel oncogenic driver in non-small cell lung cancer (NSCLC). Lorlatinib, a third-generation ALK inhibitor, exhibited a dramatic clinical response in a NSCLC patient harboring CLIP1-LTK fusion. However, it is expected that acquired resistance will inevitably develop, particularly by LTK mutations, as observed in NSCLC induced by oncogenic tyrosine kinases treated with corresponding tyrosine kinase inhibitors (TKIs). In this study, we evaluate eight LTK mutations corresponding to ALK mutations that lead to on-target resistance to lorlatinib. All LTK mutations show resistance to lorlatinib with the L650F mutation being the highest. In vitro and in vivo analyses demonstrate that gilteritinib can overcome the L650F-mediated resistance to lorlatinib. In silico analysis suggests that introduction of the L650F mutation may attenuate lorlatinib-LTK binding. Our study provides preclinical evaluations of potential on-target resistance mutations to lorlatinib, and a novel strategy to overcome the resistance.

Mechanisms of Resistance to Tyrosine Kinase Inhibitors in ROS1 Fusion-Positive Nonsmall Cell Lung Cancer.

BACKGROUND: ROS1 fusion-positive (ROS1+) nonsmall cell lung cancer (NSCLC) patients are highly sensitive to tyrosine kinase inhibitor (TKI) treatments. However, acquired TKI resistance remains the major hurdle preventing patients from experiencing prolonged benefits. METHODS: 107 advanced or metastatic ROS1+ NSCLC patients who progressed on crizotinib and lorlatinib were recruited. Tissue and plasma samples were collected at baseline (N = 50), postcrizotinib (N = 91), and postlorlatinib (N = 21), which were all subject to the 139-gene targeted next-generation DNA sequencing. Molecular dynamics modeling was performed to investigate the effects of ROS1 mutations on binding to different TKIs. RESULTS: In patients with postcrizotinib and postlorlatinib samples, an accumulation of on- and off-target resistance alterations after multiple TKI treatments was observed. ROS1 G2032R and MET amplification were the most common on-target and off-target alterations, respectively. Patients with CD74-ROS1 and SLC34A2-ROS1 had longer progression-free survival (PFS) (P < 0.001) and higher rates of resistance mutations (on-target, P = 0.001; off-target, P = 0.077) than other ROS1 fusion variants following crizotinib treatment. Ten distinct on-target resistance mutations were detected after TKI therapies, of which 4 were previously unreported (ROS1 L2010M, G1957A, D1988N, L1982V). Molecular dynamics simulations showed that all 4 mutations were refractory to crizotinib, while G1957A, D1988N, and L1982V were potentially sensitive to lorlatinib and entrectinib. CONCLUSIONS: This study provided a comprehensive portrait of TKI-resistance mechanisms in ROS1+ NSCLC patients. Using in silico simulations of TKI activity, novel secondary mutations that may confer TKI resistance were identified and may support clinical therapeutic decision-making.

Dissecting the role of ALK double mutations in drug resistance to lorlatinib with in-depth theoretical modeling and analysis.

Anaplastic lymphoma kinase (ALK) is implicated in the genesis of multiple malignant tumors. Lorlatinib stands out as the most advanced and effective inhibitor currently used in the clinic for the treatment of ALK-positive non-small cell lung cancer. However, resistance to lorlatinib has inevitably manifested over time, with double/triple mutations of G1202, L1196, L1198, C1156 and I1171 frequently observed in clinical practice, and tumors regrow within a short time after treatment with lorlatinib. Therefore, elucidating the mechanism of resistance to lorlatinib is paramount in paving the way for innovative therapeutic strategies and the development of next-generation drugs. In this study, we leveraged multiple computational methodologies to delve into the resistance mechanisms of three specific double mutations of ALKG1202R/L1196M, ALKG1202R/L1198F and ALKI1171N/L1198F to lorlatinib. We analyzed these mechanisms through qualitative (PCA, DCCM) and quantitative (MM/GBSA, US) kinetic analyses. The qualitative analysis shows that these mutations exert minimal perturbations on the conformational dynamics of the structural domains of ALK. The energetic and structural assessments show that the van der Waals interactions, formed by the conserved residue Leu1256 within the ATP-binding site and the residues Glu1197 and Met1199 in the hinge domain with lorlatinib, play integral roles in the occurrence of drug resistance. Furthermore, the US simulation results elucidate that the pathways through which lorlatinib dissociates vary across mutant systems, and the distinct environments during the dissociation process culminate in diverse resistance mechanisms. Collectively, these insights provide important clues for the design of novel inhibitors to combat resistance.

SHP2 Inhibition with TNO155 Increases Efficacy and Overcomes Resistance of ALK Inhibitors in Neuroblastoma.

Survival rates among patients with high-risk neuroblastoma remain low and novel therapies for recurrent neuroblastomas are required. ALK is commonly mutated in primary and relapsed neuroblastoma tumors and ALK tyrosine kinase inhibitors (TKI) are promising treatments for ALK-driven neuroblastoma; however, innate or adaptive resistance to single-agent ALK-TKIs remain a clinical challenge. Recently, SHP2 inhibitors have been shown to overcome ALK-TKI resistance in lung tumors harboring ALK rearrangements. Here, we have assessed the efficacy of the SHP2 inhibitor TNO155 alone and in combination with the ALK-TKIs crizotinib, ceritinib, or lorlatinib for the treatment of ALK-driven neuroblastoma using in vitro and in vivo models. In comparison to wild-type, ALK-mutant neuroblastoma cell lines were more sensitive to SHP2 inhibition with TNO155. Moreover, treatment with TNO155 and ALK-TKIs synergistically reduced cell growth and promoted inactivation of ALK and MAPK signaling in ALK-mutant neuroblastoma cells. ALK-mutant cells engrafted into larval zebrafish and treated with single agents or dual SHP2/ALK inhibitors showed reduced growth and invasion. In murine ALK-mutant xenografts, tumor growth was likewise reduced or delayed, and survival was prolonged upon combinatorial treatment of TNO155 and lorlatinib. Finally, we show that lorlatinib-resistant ALK-F1174L neuroblastoma cells harbor additional RAS-MAPK pathway alterations and can be resensitized to lorlatinib when combined with TNO155 in vitro and in vivo. Our results report the first evaluation of TNO155 in neuroblastoma and suggest that combinatorial inhibition of ALK and SHP2 could be a novel approach to treating ALK-driven neuroblastoma, potentially including the increasingly common tumors that have developed resistance to ALK-TKIs. SIGNIFICANCE: These findings highlight the translatability between zebrafish and murine models, provide evidence of aberrant RAS-MAPK signaling as an adaptive mechanism of resistance to lorlatinib, and demonstrate the clinical potential for SHP2/ALK inhibitor combinations for the treatment of ALK-mutant neuroblastoma, including those with acquired tolerance or potentially resistance to ALK-TKIs.

Second-trimester medical abortion after exposure to lorlatinib during early pregnancy, a case report.

Use of Lorlatinib, a third-generation tyrosine kinase inhibitor currently indicated in the treatment of non-small-cell lung cancer (NSCLC) with ALK or ROS1 gene fusion, is formally contra-indicated during pregnancy due to teratogenic effects observed during pre-clinical studies. We report the case of a 38-year-old woman with a ROS1-positive NSCLC, successfully treated with lorlatinib as second line therapy, who became pregnant while on treatment. Due to significant disease progression 12 weeks after lorlatinib stop and the great uncertainty on the pregnancy outcome, she finally decided to interrupt the pregnancy at 22 weeks of gestation. Echography and gross infant examination did not reveal any malformation. Pregnancies occurring under this kind of new oncologic treatment is expected to happen more frequently in the future. It seems therefore important to us to report any information on the topic to increase our level of knowledge and improve decision-making.

Molecular determinants of the response of cancer cells towards geldanamycin and its derivatives.

Geldanamycin is an ansamycin-derivative of a benzoquinone isolated from Streptomyces hygroscopicus. It inhibits tyrosine kinases and heat shock protein 90 (HSP90). Geldanamycin and 11 derivatives were subjected to molecular docking to HSP90, and 17-desmethoxy-17-N,N-dimethylamino-geldanamycin (17-DMAG) was the compound with the highest binding affinity (-7.73 ± 0.12 kcal/mol) and the lowest inhibition constant (2.16 ± 0.49 µM). Therefore, 17-DMAG was selected for further experiments in comparison to geldanamycin. Multidrug resistance (MDR) represents a major problem for successful cancer therapy. We tested geldanamycin and 17-DMAG against various drug-resistant cancer cell lines. Although geldanamycin and 17-DMAG inhibited the proliferation in all cell lines tested, multidrug-resistant P-glycoprotein-overexpressing CEM/ADR5000 cells were cross-resistant, ΔEGFR-overexpressing tumor cells and p53 knockout cells were sensitive to these two compounds. COMPARE and hierarchical cluster analyses were performed, and 60 genes were identified to predict the sensitivity or resistance of 59 NCI tumor cell lines towards geldanamycin and 17-DMAG. The distribution of cell lines according to their mRNA expression profiles indicated sensitivity or resistance to both compounds with statistical significance. Moreover, bioinformatic tools were used to study possible mechanisms of action of geldanamycin and 17-DMAG. Galaxy Cistrome analyses were carried out to predict transcription factor binding motifs in the promoter regions of the candidate genes. Interestingly, the NF-ĸB DNA binding motif (Rel) was identified as the top transcription factor. Furthermore, these 60 genes were subjected to Ingenuity Pathway Analysis (IPA) to study the signaling pathway interactions of these genes. Interestingly, IPA also revealed the NF-ĸB pathway as the top network among these genes. Finally, NF-ĸB reporter assays confirmed the bioinformatic prediction, and both geldanamycin and 17-DMAG significantly inhibited NF-κB activity after exposure for 24 h. In conclusion, geldanamycin and 17-DMAG exhibited cytotoxic activity against different tumor cell lines. Their activity was not restricted to HSP90 but indicated an involvement of the NF-KB pathway.

Cascade Transformation of the Ansamycin Benzoquinone Core into Benzoxazole Influencing Anticancer Activity and Selectivity.

The metal-free cascade transformation of geldanamycin benzoquinone core is proposed at relatively mild conditions. This approach yields new benzoxazole ansamycin antibiotics and enables their functionalization in an atom-economic manner, irrespective of the type of amine used. The analysis of the heterocyclization course reveals the dependence of its rate on the nature of the para-substituent within the benzylamine moiety (EDG/EWG) and the strength of the base. The reduction of the ansamycin core enables an increase in anticancer potency and selectivity.

Discovery of imidazo[1,2-b]pyridazine macrocyclic derivatives as novel ALK inhibitors capable of combating multiple resistant mutants.

Anaplastic lymphoma kinase (ALK)-tyrosine kinase inhibitor (TKI) often loses effectiveness against non-small cell lung malignancies (NSCLCs) with ALK gene rearrangements (ALK+). 19 novel imidazo[1,2-b]pyridazine macrocyclic derivatives were designed, synthesized, and tested for their biological activities in an effort to develop ALK inhibitors that would overcome second-generation ALK-TKIs, particularly the G1202R mutation and the lorlatinib-resistant L1196M/G1202R double mutations. Of all the target substances, O-10 had the most effective enzymatic inhibitory activity, with IC50 values for ALKWT, ALKG1202R, and ALKL1196M/G1202R of 2.6, 6.4, and 23 nM, respectively. O-10, on the other hand, reduced the growth of ALK-positive Karpas299, BaF3-EML4-ALKG1202R, and BaF3-EML4-ALKL1196M/G1202R cells with IC50 values of 38, 52, and 64 nM, respectively. This was equally effective to the reference drug Repotrectinib (IC50 = 40, 164, and 208 nM). The kinase selectivity profile, liver microsome stability test and in vivo pharmacokinetic properties in SD rats of compound O-10 were further evaluated. O-10 was regarded as an effective ALK inhibitor for the treatment of mutations overall.

Asymmetric Total Synthesis of Cytotrienin A: Late-Stage Installation of C11 Side Chain onto the Macrolactam Scaffold.

Cytotrienin A, an ansamycin-class antibiotic, exhibits potent apoptosis-inducing activity and has attracted much attention as a lead compound for anticancer drugs. Herein, we report a new asymmetric synthetic route to cytotrienin A, employing an unexplored approach involving the late-stage installation of a C11 side chain onto the macrolactam core. In this strategy, we utilized the redox properties of hydroquinone and installed a side chain on the sterically hindered C11 hydroxy group by the traceless Staudinger reaction. This study also demonstrated that the boron-Wittig/iterative Suzuki-Miyaura cross-coupling sequence was effective for the concise and selective construction of the (E,E,E)-conjugated triene moiety. The developed route opens new opportunities for the structure-activity relationship studies of the side chains of these ansamycin antibiotics and the preparation of other synthetic analogs and chemical probes for further biological studies.

HSP90-regulated CHIP/TRIM21/p21 Axis Involves in the Senescence of Osteosarcoma Cells.

BACKGROUND: OS is the most frequent malignant bone tumor with a poor prognosis. TRIM21 has been reported to play a critical role in OS by regulating the expression of the TXNIP/p21 axis and inhibiting the senescence of OS cells. AIM: Investigation of the molecular mechanism of tripartite motif 21 (TRIM21) in osteosarcoma (OS) would shed light on the understanding of the pathogenesis of OS. OBJECTIVE: This study aimed to explore the mechanism regulating the protein stability of TRIM21 in the process of OS senescence. METHODS: Human U2 OS cells were used to establish stable cells overexpressing TRIM21 (induced by Dox) or knocking down TRIM21. The co-immunoprecipitation (co-IP) assay was used to examine the interaction between TRIM21 and HSP90. Immunofluorescence (IF) assay was used to observe colocalization in OS cells. Western blot analysis was applied to detect the protein expression, and quantitative real-time PCR (qRT-PCR) assay was used to test the mRNA expression of corresponding genes. SA-ß-gal staining was used to evaluate OS senescence. RESULTS: In this study, we verified the interaction between HSP90 and TRIM21 using a co-IP assay. Knockdown or inhibition of HSP90 with its inhibitor 17-AAG accelerated the degradation of TRIM21 by the proteasome in OS cells. CHIP E3 ligase mediated this degradation of TRIM21, with the knockdown of CHIP rescuing the downregulation of TRIM21 induced by 17-AAG. TRIM21 inhibited OS senescence and downregulated the expression of senescence marker p21, while CHIP exhibited an opposite regulatory role on p21 expression. CONCLUSION: Taken together, our results demonstrated that HSP90 is responsible for the stabilization of TRIM21 in OS and that the CHIP/TRIM21/p21 axis controlled by HSP90 affects the senescence of OS cells.

Combination Therapies Targeting ALK-aberrant Neuroblastoma in Preclinical Models.

PURPOSE: ALK-activating mutations are identified in approximately 10% of newly diagnosed neuroblastomas and ALK amplifications in a further 1%-2% of cases. Lorlatinib, a third-generation anaplastic lymphoma kinase (ALK) inhibitor, will soon be given alongside induction chemotherapy for children with ALK-aberrant neuroblastoma. However, resistance to single-agent treatment has been reported and therapies that improve the response duration are urgently required. We studied the preclinical combination of lorlatinib with chemotherapy, or with the MDM2 inhibitor, idasanutlin, as recent data have suggested that ALK inhibitor resistance can be overcome through activation of the p53-MDM2 pathway. EXPERIMENTAL DESIGN: We compared different ALK inhibitors in preclinical models prior to evaluating lorlatinib in combination with chemotherapy or idasanutlin. We developed a triple chemotherapy (CAV: cyclophosphamide, doxorubicin, and vincristine) in vivo dosing schedule and applied this to both neuroblastoma genetically engineered mouse models (GEMM) and patient-derived xenografts (PDX). RESULTS: Lorlatinib in combination with chemotherapy was synergistic in immunocompetent neuroblastoma GEMM. Significant growth inhibition in response to lorlatinib was only observed in the ALK-amplified PDX model with high ALK expression. In this PDX, lorlatinib combined with idasanutlin resulted in complete tumor regression and significantly delayed tumor regrowth. CONCLUSIONS: In our preclinical neuroblastoma models, high ALK expression was associated with lorlatinib response alone or in combination with either chemotherapy or idasanutlin. The synergy between MDM2 and ALK inhibition warrants further evaluation of this combination as a potential clinical approach for children with neuroblastoma.

Genomic and Spectroscopic Signature-Based Discovery of Natural Macrolactams.

The logical and effective discovery of macrolactams, structurally unique natural molecules with diverse biological activities, has been limited by a lack of targeted search methods. Herein, a targeted discovery method for natural macrolactams was devised by coupling genomic signature-based PCR screening of a bacterial DNA library with spectroscopic signature-based early identification of macrolactams. DNA library screening facilitated the efficient selection of 43 potential macrolactam-producing strains (3.6% of 1,188 strains screened). The PCR amplicons of the amine-deprotecting enzyme-coding genes were analyzed to predict the macrolactam type (α-methyl, α-alkyl, or ß-methyl) produced by the hit strains. 1H-15N HSQC-TOCSY NMR analysis of 15N-labeled culture extracts enabled macrolactam detection and structural type assignment without any purification steps. This method identified a high-titer Micromonospora strain producing salinilactam (1), a previously reported α-methyl macrolactam, and two Streptomyces strains producing new α-alkyl and ß-methyl macrolactams. Subsequent purification and spectroscopic analysis led to the structural revision of 1 and the discovery of muanlactam (2), an α-alkyl macrolactam with diene amide and tetraene chromophores, and concolactam (3), a ß-methyl macrolactam with a [16,6,6]-tricyclic skeleton. Detailed genomic analysis of the strains producing 1-3 identified putative biosynthetic gene clusters and pathways. Compound 2 displayed significant cytotoxicity against various cancer cell lines (IC50 = 1.58 µM against HCT116), whereas 3 showed inhibitory activity against Staphylococcus aureus sortase A. This genomic and spectroscopic signature-based method provides an efficient search strategy for new natural macrolactams and will be generally applicable for the discovery of nitrogen-bearing natural products.

Lorlatinib beyond progression plus platinum/pemetrexed for ALK-positive non-small cell lung cancer patients: report of two cases.

Lorlatinib is an active treatment for advanced anaplastic lymphoma kinase (ALK)-positive non-small cell lung cancer (NSCLC) pretreated with ALK-tyrosine kinase inhibitors (-TKIs). However, there is paucity of data on the activity of platinum/pemetrexed chemotherapy administered at the time of progression on lorlatinib. In addition, it is uncertain whether continuation of lorlatinib beyond progression (LBP) would provide any additional clinical benefit. Here, we describe two cases experiencing an exceptional response to platinum/pemetrexed chemotherapy plus LBP and make an attempt to identify which patients' characteristics and biologic profiles of the tumor could predict benefit from such an approach. In this report, presence of controlled brain metastases, rapidly progressing extracranial disease, and presence of ALK-dependent mechanisms of resistance were associated with benefit from platinum/pemetrexed chemotherapy plus lorlatinib beyond progression.

HSP90ß chaperoning SMURF1-mediated LATS proteasomal degradation in the regulation of bone formation.

Heat shock protein 90 (HSP90) molecular chaperone is responsible for the stabilization and biological activity of a diverse set of client proteins. We have previously demonstrated that inhibition of HSP90 by 17-Demethoxy-17-allyaminogeldanmycin (17-AAG) not only reverses the glucocorticoid-induced bone loss but also enhances the basal level of bone mass in mice. Here, we investigate the potential mechanism underlying HSP90-associated osteoblast differentiation and bone formation. Knockdown of HSP90ß but not HSP90α or inhibition of HSP90 by 17-AAG or NVP-BEP800 negates the protein levels of large tumor suppressor (LATS), the core kinases of Hippo signaling, resulting in the inactivation of LATS and activation of Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), in the enhancement of osteoblastic differentiation. In contrast, genetic ablation of Lats1 in mesenchymal stem cells is sufficient to abolish the HSP90 inhibition-induced osteoblastic differentiation and bone formation. Mechanistically, HSP90ß but not HSP90α chaperones and prevents the SMAD specific E3 ubiquitin protein ligase 1 (SMURF1)-mediated and ubiquitination-dependent LATS protein proteasomal degradation, whereas 17-AAG abolishes these effects of HSP90ß. Thus, these results uncover the HSP90ß chaperoning SMURF1-mediated LATS protein proteasomal degradation and the subsequent YAP/TAZ activation as a hitherto uncharacterized mechanism controlling osteoblastic differentiation and bone formation.

NVL-520 Is a Selective, TRK-Sparing, and Brain-Penetrant Inhibitor of ROS1 Fusions and Secondary Resistance Mutations.

SIGNIFICANCE: The combined preclinical features of NVL-520 that include potent targeting of ROS1 and diverse ROS1 resistance mutations, high selectivity for ROS1 G2032R over TRK, and brain penetration mark the development of a distinct ROS1 TKI with the potential to surpass the limitations of earlier-generation TKIs for ROS1 fusion-positive patients. This article is highlighted in the In This Issue feature, p. 517.

Lorlatinib and compound mutations in ALK+ large-cell neuroendocrine lung carcinoma: a case report.

Large-cell neuroendocrine lung carcinoma (LCNEC) is a high-grade neoplasm with median survival of 1 year and limited therapeutic options. Here, we report the unusual case of a 47-yr-old female smoker with stage IV LCNEC featuring EML4-ALK variant 2 (E20:A20), wild-type TP53/RB1, and low tumor mutational burden of 3.91 mut/Mb. Despite early progression within 3 mo under crizotinib, a durable response was achieved with alectinib. Oligoprogression in the left breast 10 mo later was treated by surgery, followed by a switch to ceritinib upon multifocal progression and detection of ALK:p.V1180L in the mastectomy specimen, but without success. Another rebiopsy revealed ALK:p.L1196M, but the tumor did not respond to brigatinib or carboplatin/pemetrexed, before stabilization under lorlatinib. Diffuse progression 8 mo later with detection of ALK :p.L1196M/p.G1202R and p.L1196M/ p.D1203N evolving from the previous p.L1196M did not respond to chemoimmunotherapy, and the patient succumbed with an overall survival (OS) of 37 mo. This case illustrates the importance of molecular profiling for LCNEC regardless of smoking status, and the superiority of next-generation ALK inhibitors compared to crizotinib for ALK+ cases. Lorlatinib retained efficacy in the heavily pretreated setting, whereas its upfront use could possibly have prevented the stepwise emergence of compound ALK mutations. Furthermore, the disease course was more aggressive and OS shorter compared to the V2/TP53wt ALK+ lung adenocarcinoma, whereas crizotinib, ceritinib, and brigatinib did not confer the benefit expected according to next-generation sequencing results, which also underline the need for more potent drugs against ALK in the high-risk setting of neuroendocrine histology.

Inhibition of Hsp90 during in vitro maturation under thermoneutral or heat shock conditions compromises the developmental competence of bovine oocytes.

Heat shock protein 90 (Hsp90) is critical for cell homeostasis but its role on bovine oocyte maturation is not well known. We investigated the importance of Hsp90 for competence of bovine oocyte using 17-(allylamino)-17-demethoxygeldanamycin (17AAG), an inhibitor of Hsp90, during in vitro maturation (IVM). Three experiments evaluated the effect of 17AAG on developmental competence of oocytes matured in vitro under thermoneutral (38.5ºC) or heat shock (HS; 41.5ºC) temperatures. The first experiment found that the blastocyst rates were lower (P < 0.05) with 2 µM 17AAG compared with the untreated control (0 µM). The abundance of HSF1 transcripts was higher in oocytes matured with 2 µM than with 0 and 1 µM 17AAG, whereas the abundance of HSP90AA1 and HSPA1A transcripts was lower (P < 0.05) with 1 and 2 µM than with 0 µM. The second experiment found that 2 µM 17AAG for 12 or 24 h during IVM decreased (P < 0.05) the blastocysts rates. In the third experiment, the association of 2 µM 17AAG with HS for 12 h during IVM resulted in lower (P < 0.05) blastocysts rates than 17AAG, HS or untreated control. In conclusion, inhibition of Hsp90 during in vitro maturation compromises further embryo development; the association of Hsp90 inhibition with HS aggravates the deleterious effect of both on oocyte developmental competence.

Acquired G2032R Resistance Mutation in ROS1 to Lorlatinib Therapy Detected with Liquid Biopsy.

Lorlatinib, a third-generation anaplastic lymphoma kinase (ALK)/receptor tyrosine kinase inhibitor (ROS1), demonstrated efficacy in ROS1 positive (ROS1+) non-small cell lung cancer (NSCLC), although approval is currently limited to the treatment of ALK+ patients. However, lorlatinib-induced resistance mechanisms, and its efficacy against the resistance mutation G2032R in ROS1, respectively, have not yet been fully understood. Furthermore, concomitant tumor suppressor gene p53 (TP53) mutations occur in driver alteration positive NSCLC, but their prognostic contribution in the context of ROS1 inhibition remains unclear. Here we report a ROS1+ NSCLC patient who developed an on target G2032R resistance mutation during second-line lorlatinib treatment, indicating the lack of activity of lorlatinib against ROS1 G2032R. The resistance mutation was detected in plasma-derived ctDNA, signifying the clinical utility of liquid biopsies.