Enhanced effect of checkpoint inhibitors when given after or together with IMM-101: significant responses in four advanced melanoma patients with no additional major toxicity.

BACKGROUND: The use of checkpoint inhibitors (ipilimumab, pembrolizumab, nivolumab) has revolutionised the treatment of metastatic melanoma. However still more than the half the patients do not respond to single-agent immunotherapy. This has led to the development of combining these agents in an attempt to enhance the anti-cancer activity. More than 300 different studies with 15 different drug doses are currently ongoing. Combining different checkpoint inhibitors (CPIs) does indeed lead to an increase in response rate, but this is associated with significant toxicity. IMM-101 is a heat killed Mycobacterium preparation which induces marked immune modulation and little systemic toxicity. It has been reported as having activity in melanoma as single agent and in pancreatic cancer in combination with gemcitabine, the latter in a randomised study. METHODS: Here we report the effect of adding CPIs to 3 patients who had previously been on IMM-101, either as a trial or a named patient programme and a patient who received the IMM-101 together with nivolumab. RESULTS: All 4 patients had rapid and very good responses, three of them maintained over 18 months with no significant additional toxicity. CONCLUSIONS: The rapid and complete clinical responses seen in these patients may suggest that IMM-101 is activating a complementary pathway which is synergistic with CPI treatment.

The importance for immunoregulation for long-term cancer control.

Immune checkpoint blockades have recently emerged as a breakthrough treatment for solid tumors showing high response rates and long durability. In melanoma, the combination of ipilimumab with nivolumab showed high efficacy. However, still half the patients do not respond to this treatment. In order to increase the therapeutic ratio in melanoma and other cancers, different approaches are under evaluation. Three relevant questions are at the moment driving the research community: how to maximize benefit while minimizing toxicity; how to better identify patients who are more likely to benefit from immunotherapy; how to convert nonresponders into responders. In this review we summarize the most recent findings and we outline the most likely future challenges.

A randomised phase 2 study of intermittent versus continuous dosing of dabrafenib plus trametinib in patients with BRAFV600 mutant advanced melanoma (INTERIM).

BACKGROUND: BRAF+MEK inhibitors extend life expectancy of patients with BRAFV600 mutant advanced melanoma. Acquired resistance limits duration of benefit, but preclinical and case studies suggest intermittent dosing could overcome this limitation. INTERIM was a phase 2 trial evaluating an intermittent dosing regimen. METHODS: Patients with BRAFV600 mutant advanced melanoma due to start dabrafenib+trametinib were randomised to receive either continuous (CONT), or intermittent (INT; dabrafenib d1-21, trametinib d1-14 every 28 days) dosing. A composite primary endpoint included progression-free survival (PFS) and quality of life (QoL). Secondary endpoints included response rate (ORR), overall survival (OS) and adverse events (AEs). Mutant BRAFV600E ctDNA was measured by droplet digital PCR (ddPCR), using mutant allele frequency of > 1 % as the detection threshold. RESULTS: 79 patients (39 INT, 40 CONT) were recruited; median age 67 years, 65 % AJCC (7th ed) stage IV M1c, 29 % had brain metastases. With 19 months median follow-up, INT was inferior in all efficacy measures: median PFS 8.5 vs 10.7mo (HR 1.39, 95 %CI 0.79-2.45, p = 0.255); median OS 18.1mo vs not reached (HR 1.69, 95 %CI 0.87-3.28, p = 0.121), ORR 57 % vs 77 %. INT patients experienced fewer treatment-related AEs (76 % vs 88 %), but more grade > 3 AEs (53 % vs 42 %). QoL favoured CONT. Detection of BRAFV600E ctDNA prior to treatment correlated with worse OS (HR 2.55, 95 %CI 1.25-5.21, p = 0.01) in both arms. A change to undetected during treatment did not significantly predict better OS. CONCLUSION: INTERIM findings are consistent with other recent clinical trials reporting that intermittent dosing does not improve efficacy of BRAF+MEK inhibitors.

Analysis of surrogate gene expression markers in peripheral blood of melanoma patients to predict treatment outcome of adjuvant pegylated interferon alpha 2b (EORTC 18991 side study).

We analysed mRNA levels of interferon response genes (ISG15, STAT1, CXCL10) of inhibitors of the JAK/STAT pathway (STAT3, SOCS1, SOCS3) and of cytokines (TNFα, IL10, TGFß1) in peripheral blood of 91 stage III melanoma patients enrolled in EORTC 18991 trial to find biomarkers indicative for disease stage and predictive for efficacy of pegylated interferon alpha-2b (PEG-IFNα-2b) therapy. mRNA levels were analysed at baseline and after 6 months. Univariate and multivariate analyses were performed to estimate the prognostic and predictive role of mRNA levels for distant metastasis-free survival (DMFS) and relapse-free survival (RFS). Compared to healthy controls, melanoma patients showed significantly higher TGFß1 mRNA levels. In a multivariate model, increasing SOCS1 and SOCS3 mRNA levels were associated with worse RFS (P = 0.02 and P = 0.04, respectively) and DMFS (P = 0.05 and P = 0.05, respectively) due to negative correlation between, respectively, SOCS1/SOCS3 mRNA levels and ulceration or Breslow thickness. No impact of PEG-IFNα-2b on mRNA levels was observed except for ISG15 mRNA levels, which decreased in the treatment arm (P = 0.001). It seems that patients with a decrease >60 % of ISG15 mRNA levels during 6 months PEG-IFNα-2b had inferior outcome.

Clinical utility of circulating tumour cell detection in non-small-cell lung cancer.

OPINION STATEMENT: Recent years have witnessed increased interest in the detection of circulating tumour cells (CTCs) for diagnosis, monitoring, and treatment decision making in patients with cancer. Factors that have led to accelerated research in this field include advances in technologies for examination of intact CTCs, personalised medicine with treatment selection according to molecular characteristics, and continued lack of understanding of the biology of treatment resistance and metastasis. CTCs offer promise as a surrogate for tissue where there is insufficient tissue for molecular analysis and where there is a requirement to serially monitor molecular changes in cancer cells through treatment or on progression. In patients with either small cell or non-small cell lung cancer (NSCLC), there is evidence that CTC number is prognostic and that CTCs counted before and after treatment mirror treatment response. In patients with molecularly defined subtypes of NSCLC, CTCs demonstrate the same molecular changes as the cancer cells of the tumour. However, CTCs are not quite ready for "primetime" in the lung cancer clinic. There are still more questions than answers with respect to the optimal technologies for their detection and analysis, their biological significance, and their clinical utility. Despite this the current pace of progress in CTC technology development seems set to make "liquid biopsies" a clinical reality within the next decade. For the everyday clinician and clinical trialist, it will be important to maintain knowledge of the strengths and weaknesses of the technologies and evolving evidence base for CTCs as a routinely used diagnostic tool.

Wilms' tumor protein 1 (WT1) peptide vaccination in AML patients: predominant TCR CDR3ß sequence associated with remission in one patient is detectable in other vaccinated patients.

BACKGROUND: Clinically effective T-cell responses can be elicited by single peptide vaccination with Wilms' tumor 1 (WT1) epitope 126-134 in patients with acute myeloid leukemia (AML). We recently showed that a predominant T-cell receptor (TCR) ß chain was associated with vaccine-induced complete remission in an AML patient (patient 1). In this study, we address the question of whether this predominant clone or the accompanying Vß11 restriction could be found in other AML patients vaccinated with the same WT1 peptide. MATERIALS AND METHODS: For assessment of Vß usage, cytotoxic T lymphocytes (CTLs) from four vaccinated patients were divided into specific and non-specific by epitope-specific enrichment. Vß families were quantified in both fractions using reverse transcribed quantitative PCR. Vß11-positive 'complementary determining region 3' (CDR3) sequences were amplified from these samples, from bone marrow samples of 17 other vaccination patients, and from peripheral blood of six healthy controls, cloned and sequenced. RESULTS: We observed a clear bias towards Vß11 usage of the WT1-specific CTL populations in all four patients. The predominant CDR3ß amino acid (AA) sequence of patient 1 was detected in two other patients. CDR3ß loops with closely related AA sequences were only found in patient 1. There were no CDR3ß AA sequences with side chains of identical chemical properties detected in any patient. CONCLUSION: We provide the first data addressing TCR Vß chain usage in WT1-specific T-cell populations after HLA A*0201-restricted single peptide vaccination. We demonstrate both shared Vß restriction and the sharing of a TCR ß transcript with proven clinical impact in one patient.

Expression of chemokine receptors on circulating tumor cells in patients with solid tumors.

BACKGROUND: The study was performed to investigate the expression of chemokine receptors (CR) on circulating tumor cells (CTC), which may be of importance for organ-specific metastases and cancer treatment since CR are potential drug-targets. METHODS: Blood samples from patients with metastatic carcinoma (MC) or melanoma (MM) were enriched for CTC and expression of CR (CXCR4, CCR6, CCR7 and CCR9) was evaluated by flow cytometry. RESULTS: CTC were detected in 49 of 68 patients (72%) [28 MC; 21 MM] with a median number of 3 CTC (range: 1-94)/10 mL of blood. CXCR4 was expressed on CTC in 82% (40/49) of patients [median number 1 CTC/10 mL blood; range 1-14] and CCR6 in 29 patients (59%; median 1, range: 1-14). In MM patients, CCR7 was expressed on CTC in 6 (29%) samples and CCR9 in 12 (57%). A positive correlation between surface expression of CR and organ-specific metastatic pattern was not observed. CONCLUSIONS: CR were expressed on CTC of patients with solid tumors. Along with our findings, the observation that CR could be involved in CTC proliferation and migration of tumor cells appoints CTC as potential CR-antagonist therapeutic target.

In vitro and in vivo antitumor activity of cetuximab in human gastric cancer cell lines in relation to epidermal growth factor receptor (EGFR) expression and mutational phenotype.

BACKGROUND: Targeting the epidermal growth factor receptor (EGFR) pathway is an important approach for a variety of tumors. This study assessed the effect of cetuximab, an anti-EGFR monoclonal antibody, on three gastric cancer cell lines with different phenotypes in vitro and in a therapeutic orthotopic murine gastric cancer model. METHODS: Three human gastric cancer cell lines (AGS, MKN-45, NCI-N87) were evaluated for cell surface EGFR expression, and K-ras and BRAF mutations. In vitro, the effects of cetuximab, carboplatin, irinotecan, and docetaxel were investigated. Orthotopic tumors derived from MKN-45 and NCI-N87 were established in nude mice. After 4 weeks, the animals received cetuximab (1 mg/kg, weekly i.p.) or carboplatin (20 mg/kg, weekly i.p.), or both agents. The volume of the primary tumor and local and systemic tumor spread were determined at autopsy at 14 weeks. Tumor sections were immunostained for EGFR, as well as stained for CD31 to analyze microvessel density. RESULTS: Cell surface expression of EGFR was found only in AGS and NCI-N87 cells. AGS cells displayed a codon 12 K-ras mutation, and all three cell lines were BRAF wild-type. In vitro, cetuximab significantly reduced cell viability and proliferation only in EGFR-positive/K-ras wild-type NCI-N87 cells (-48%). In vivo, cetuximab in combination with carboplatin synergistically reduced tumor volume (-75%), dissemination (-63%), and vascularization (-47%) in NCI-N87 xenografts. Tumors derived from EGFR-negative MKN-45 cells were unaffected by cetuximab. CONCLUSIONS: Cetuximab is effective in K-ras wild-type, EGFR-expressing gastric cancer cell lines and xenografts. In vivo, the combination of cetuximab with carboplatin displayed synergistic antitumor activity.

Negative enrichment by immunomagnetic nanobeads for unbiased characterization of circulating tumor cells from peripheral blood of cancer patients.

BACKGROUND: A limitation of positive selection strategies to enrich for circulating tumor cells (CTCs) is that there might be CTCs with insufficient expression of the surface target marker which may be missed by the procedure. We optimized a method for enrichment, subsequent detection and characterization of CTCs based on depletion of the leukocyte fraction. METHODS: The 2-step protocol was developed for processing 20 mL blood and based on red blood cell lysis followed by leukocyte depletion. The remaining material was stained with the epithelial markers EpCAM and cytokeratin (CK) 7/8 or for the melanoma marker HMW-MAA/MCSP. CTCs were detected by flow cytometry. CTCs enriched from blood of patients with carcinoma were defined as EpCAM+CK+CD45-. CTCs enriched from blood of patients with melanoma were defined as MCSP+CD45-. One-hundred-sixteen consecutive blood samples from 70 patients with metastatic carcinomas (n = 48) or metastatic melanoma (n = 22) were analyzed. RESULTS: CTCs were detected in 47 of 84 blood samples (56%) drawn from carcinoma patients, and in 17 of 32 samples (53%) from melanoma patients. CD45-EpCAM-CK+ was detected in pleural effusion specimens, as well as in peripheral blood samples of patients with NSCLC. EpCAM-CK+ cells have been successfully cultured and passaged longer than six months suggesting their neoplastic origin. This was confirmed by CGH. By defining CTCs in carcinoma patients as CD45-CK+ and/or EpCAM+, the detection rate increased to 73% (61/84). CONCLUSION: Enriching CTCs using CD45 depletion allowed for detection of epithelial cancer cells not displaying the classical phenotype. This potentially leads to a more accurate estimation of the number of CTCs. If detection of CTCs without a classical epithelial phenotype has clinical relevance need to be determined.

Life-threatening polymyositis with spontaneous hematoma induced by nivolumab in a patient with previously resected melanoma.

Single-agent anti-PD1 antibodies are usually very well tolerated, but serious toxicity can still occur. Despite the PD-1 pathway seems to be relevant in the pathogenesis of immune-related myositis, anti-PD1-related myositis is generally a rare side effect of the treatment and usually not serious. However, its frequency is likely to increase as the use of immune checkpoint blockades. We present here a case of life-threatening polymyositis with associated spontaneous muscular hematoma in a patient treated with single-agent nivolumab in the adjuvant setting. Spontaneous hematoma is an extremely rare complication with unclear etiology of idiopathic myositis. Very few cases have been reported in the literature and their outcome has been often fatal. To our knowledge, this is the first case of autoimmune myositis and spontaneous heamatoma associated with the administration of single-agent checkpoint blockade. Anti-PD1 antibodies have changed the treatment landscape for a number of cancer entities in the past few years. When given as single agent they are usually very well tolerated, but serious rare toxicity can still occur. We present here a case of polymyositis with associated spontaneous muscular hematoma in a patient treated with single agent nivolumab.

Long term presence of a single predominant tyrosinase-specific T-cell clone associated with disease control in a patient with metastatic melanoma.

In an earlier study, we described a patient who developed an anti-tyrosinase T-cell response leading to long-term tumor control. Here we analyzed this response with regard to T-cell receptor (TCR) Vbeta family usage and clonality in order to further elucidate the nature of the T cell response in this patient. For identification of expanded specific cytotoxic T-cell (CTL) clones, tetramer enrichment of tyrosinase reactive T-cells was followed by comparative quantitative reverse transcribed PCR (qRT PCR) quantification of all TCR Vbeta-families and sequencing of family Vbeta4 elevated in the enriched fraction. The predominant specific clone was quantified by clonotypic qRT PCR in multiple samples from blood, bone marrow, and tumor tissue. FACS analyses with staining of TYR.A2 and TCR Vbeta4 were performed. Epitope specific enrichment revealed an isolated increase of Vbeta-family 4. FACS analysis showed a shift of specific CTLs to Vbeta-family 4 during tumor regression with a maximum of 80% of all TYR.A2 specific cells belonging to this family. Sequencing revealed a single predominant clone against polyclonal background coding for identical CDR3 loops. The predominant clone was highly expressed in bone marrow and tumor tissue, and was detectable in blood over a period of ten years. Considering the results of previous studies showing a specific effector phenotype in blood and a specific memory compartment in bone marrow of this patient, this data implicate the predominant clone featured all attributes of a sufficient CTL response including homing capacity and memory formation resulting in long term clonal persistence and tumor control.

Comparison of T-cell receptor repertoire restriction in blood and tumor tissue of colorectal cancer patients.

Several immunotherapeutic approaches rely on antigen-specific T-cells. Restrictions in the T-cell receptor (TCR) repertoire were reported as indicator of anti-tumor cytotoxic T-lymphocyte (CTL) response in various tumor entities. It is unclear yet whether a TCR restriction in peripheral blood mirrors the tumor compartment. We compared the expression of TCR Vbeta-families for the quantification of TCR repertoire alterations in blood and tissue samples from patients with colorectal carcinoma. Blood samples from patients with colorectal carcinoma and healthy volunteers and tissue samples of normal colonic mucosa and colorectal carcinoma were analyzed. Relative Vbeta-family quantification was performed based on quantitative reverse transcribed PCR. Standard deviation and average mean of the single families were determined. Two variables describing the degree of Vbeta-repertoire restriction were defined. Forty-eight blood samples and 37 tissue samples were analyzed. TCR repertoire restriction was higher in blood of tumor patients than in blood of healthy controls (p < 0.05). No difference in the degree of TCR repertoire restriction was found between carcinoma and unaffected colon tissue. We found no corresponding elevated TCR families among the different compartments blood, normal colon, and carcinoma tissue of the same patient. In conclusion, we observed a repertoire restriction in peripheral blood as well as in tumor tissue of cancer patients. However, in tumor tissue, repertoire alterations were comparable to normal mucosa, suggesting compartment-specific TCR distribution rather than alterations due to tumor-T-cell interaction questioning the presence of highly restricted clonal T-cell expansions in colorectal cancer as they have been described in other, assumingly more immunogenic tumor entities.

Effect of carboplatin when administered after dacarbazine failure: Clinical benefit of sequential therapy.

Dacarbazine chemotherapy has been the mainstay of melanoma treatment for >30 years. In the early 2000s, carboplatin (with or without other agents, such as paclitaxel) was the most commonly used second-line therapy in the UK. The aim of the present study was to report a significant response rate to second-line carboplatin in patients from three UK institutions who had been previously treated and failed to respond to dacarbazine, and investigate whether sequential therapy may be more effective compared with combination therapy. A total of 104 patients were identified, the majority of whom were treated with carboplatin (area under the curve 5-6) every 3 weeks for a maximum of 6 cycles. A total of 102 patients were evaluable for response, among whom 11 patients had an objective response (1 complete response and 10 partial responses) and 15 had stable disease, giving an overall response rate of 11% and disease control rate of 26%. The median progression-free survival was 1.8 months (range, 0.2-36+ months) and the median overall survival was 4.6 months (range, 0.2-36+ months). Surprisingly, the majority of the patients who benefited from second-line carboplatin therapy were those with visceral metastases, the survival of whom would not be expected to exceed 6 months after first-line treatment.

Serum Apolipoprotein E and Other Inflammatory Markers Can Identify Non-Responding Patients to a Dendritic Cell Vaccine.

BACKGROUND: Despite the majority of patients do not gain any benefit from dendritic cells (DC) vaccines, this approach has occasionally given rise to dramatic responses in melanoma. Biomarkers are crucial to identify which patients are more likely to respond. We looked for correlations between pre- or post- vaccination biomarkers and clinical outcomes to DC therapy in a cohort of patients with stage IV melanoma receiving a vaccine with autologous ex-vivo expanded DCs pulsed with allogeneic tumor cell lysate. METHODS: Serial serum samples were collected at baseline, week 4 and 12 and they were analyzed for a panel of different inflammatory markers using cytometric bead array technology and ELISA. RESULTS: Twenty-one patients were evaluable for response. Patients were separated into responders and non-responders based on clinical benefit. Responders were defined as patients who achieved a complete response, partial response or stable disease the latter lasting for at least 6 months. Responders (N = 9) showed a significantly longer Progression-free Survival (PFS; HR 0.23; 95% CI 0.08-062; P < .001) and Overall Survival (OS; HR 0.22; 95% CI 0.08-0.59; P < .001). The clinical non-responder phenotype correlated with an elevated pre-vaccination level of cytokines associated with inflammation compared to clinical responders (Apolipoprotein C111; IL-12 p40; MiP1α; Stem Cell Factor and TNFα). Apolipoprotein E (ApoE) was also significantly elevated in the pre-vaccine sera of the clinically non-responding group and in addition it was found to correlate with outcomes. Patients with increased levels of ApoE had a significantly shorter PFS (HR 3.02; 95% CI 1.09-8.35; P = .015) and OS (HR 2.40; 95% CI 0.9-6.3; P = .034). CONCLUSION: Our findings support the notion that treating the inflammatory background may have an impact on clinical outcome for patients receiving immunotherapy. A larger study is needed to confirm the significance of ApoE as a predictive biomarker for response to DC vaccines.

Relative quantification of TCR Vbeta-chain families by real time PCR for identification of clonal T-cell populations.

BACKGROUND: Quantification of T-cell receptor (TCR) chain families can be utilized for detection of clonal T-cell populations. Besides southern blotting and antibody-based approaches, quantitative real time PCR (qRT PCR) has been more widely applied in this context during the last years. Here, the heterogeneity of sequences within single families is the most challenging problem for exact quantification. METHOD: Vbeta-families were quantified using a universal reverse primer and family-specific forward primers with TaqMan technology on a light cycler instrument. Relative concentrations were calculated considering slopes and crossing points of each PCR reaction. Total expression of alpha/beta TCR was assessed by quantification of the constant alpha-chain as a further control. RESULTS: The method was tested by serial dilutions of clonal T-cells in mononuclear cells from healthy volunteers. Calculated percentages were in good correspondence with qRT PCR results demonstrating high reliability. Duplicates showed excellent technical reproducibility. We analyzed blood samples of 20 healthy volunteers for determination of mean and standard deviation for each family. The method was applied both to tissue and blood samples from patients with carcinomas and hematological disorders. CONCLUSION: We introduce a versatile method for the relative quantification of Vbeta-families by real time PCR. The experimental strategy described allows the identification of alterations in the Vbeta-family repertoire.

Oxaliplatin doublets in non-small cell lung cancer: a literature review.

Nowadays cisplatin doublets are considered the gold-standard treatment in advanced non-small cell lung cancer (NSCLC) patients, but are often associated to poor toxicity profile. In the last years different schedules have been developed in order to improve the tolerability of these regimens. Carboplatin is gradually replacing cisplatin in clinical practice as well as in clinical trials even if it is still unclear whether it has an equivalent efficacy compared to cisplatin. Oxaliplatin, the trans-l oxalato platinum compound, showed encouraging antineoplastic activity and favourable toxicity profile in NSCLC, but confirmatory randomized phase III trials are warranted. We performed a literature search in order to better understand the possible role of oxaliplatin-based combinations in advanced NSCLC treatment strategies.

Molecular dissection of colorectal cancer in pre-clinical models identifies biomarkers predicting sensitivity to EGFR inhibitors.

Colorectal carcinoma represents a heterogeneous entity, with only a fraction of the tumours responding to available therapies, requiring a better molecular understanding of the disease in precision oncology. To address this challenge, the OncoTrack consortium recruited 106 CRC patients (stages I-IV) and developed a pre-clinical platform generating a compendium of drug sensitivity data totalling >4,000 assays testing 16 clinical drugs on patient-derived in vivo and in vitro models. This large biobank of 106 tumours, 35 organoids and 59 xenografts, with extensive omics data comparing donor tumours and derived models provides a resource for advancing our understanding of CRC. Models recapitulate many of the genetic and transcriptomic features of the donors, but defined less complex molecular sub-groups because of the loss of human stroma. Linking molecular profiles with drug sensitivity patterns identifies novel biomarkers, including a signature outperforming RAS/RAF mutations in predicting sensitivity to the EGFR inhibitor cetuximab.

Neuroendocrine tumors of the larynx: a clinical report and literature review.

Neuroendocrine tumors of the larynx represent a rare group of neoplasms characterized by pathological and biological heterogeneity. The histological diagnosis is the most important step in the appropriate management of these tumors and the prognosis varies according to histological types. Here we report on a case of a laryngeal neuroendocrine tumor occurring in a 67-year-old man who underwent several locoregional and systemic treatments. Because of the very low incidence of neuroendocrine tumors in the larynx, a review of the literature has also been performed.

Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma.

UNLABELLED: Targeted therapies and immunotherapies have transformed melanoma care, extending median survival from ∼9 to over 25 months, but nevertheless most patients still die of their disease. The aim of precision medicine is to tailor care for individual patients and improve outcomes. To this end, we developed protocols to facilitate individualized treatment decisions for patients with advanced melanoma, analyzing 364 samples from 214 patients. Whole exome sequencing (WES) and targeted sequencing of circulating tumor DNA (ctDNA) allowed us to monitor responses to therapy and to identify and then follow mechanisms of resistance. WES of tumors revealed potential hypothesis-driven therapeutic strategies for BRAF wild-type and inhibitor-resistant BRAF-mutant tumors, which were then validated in patient-derived xenografts (PDX). We also developed circulating tumor cell-derived xenografts (CDX) as an alternative to PDXs when tumors were inaccessible or difficult to biopsy. Thus, we describe a powerful technology platform for precision medicine in patients with melanoma. SIGNIFICANCE: Although recent developments have revolutionized melanoma care, most patients still die of their disease. To improve melanoma outcomes further, we developed a powerful precision medicine platform to monitor patient responses and to identify and validate hypothesis-driven therapies for patients who do not respond, or who develop resistance to current treatments.