Identification of non-adherence to adjuvant letrozole using a population pharmacokinetics approach in hormone receptor-positive breast cancer patients.

BACKGROUND: Letrozole, an aromatase inhibitor metabolised via CYP2A6 and CYP3A4/5 enzymes, is used as adjuvant therapy for women with hormone receptor (HR)-positive early breast cancer. The objective of this study was to quantify the impact of CYP2A6 genotype on letrozole pharmacokinetics (PK), to identify non-adherent patients using a population approach and explore the possibility of a relationship between non-adherence and early relapse. METHODS: Breast cancer patients enrolled in the prospective PHACS study (ClinicalTrials.gov NCT01127295) and treated with adjuvant letrozole 2.5 mg/day were included. Trough letrozole concentrations (Css,trough) were measured every 6 months for 3 years by a validated LC-MS/MS method. Concentration-time data were analysed using non-linear mixed effects modelling. Three methods were evaluated for identification of non-adherent subjects using the base PK model. RESULTS: 617 patients contributing 2534 plasma concentrations were included and led to a one-compartment PK model with linear absorption and elimination. Model-based methods identified 28 % of patients as non-adherent based on high fluctuations of their Css,trough compared to 3 % based on patient declarations. The covariate analysis performed in adherent subjects revealed that CYP2A6 intermediate (IM) and slow metabolisers (SM) had 21 % (CI95 % = 12 - 30 %) and 46 % (CI95 % = 41 - 51 %) lower apparent clearance, respectively, compared to normal and ultrarapid metabolisers (NM+UM). Early relapse (19 patients) was not associated with model-estimated, concentration-based or declared adherence in the total population (p = 0.41, p = 0.37 and p = 0.45, respectively). CONCLUSIONS: These findings will help future investigations focusing on the exposure-efficacy relationship for letrozole in adjuvant setting.

Combining Three Tyrosine Kinase Inhibitors: Drug Monitoring Is the Key.

A combination of tyrosine kinase inhibitors (TKIs) is likely to be a therapeutic option for numerous oncological situations due to high frequency of oncogenic addiction and progress in precision oncology. Non-small cell lung cancer (NSCLC) represents a subtype of tumors for which oncogenic drivers are frequently involved. To the best of our knowledge, we report the first case of a patient treated with three different TKIs. Osimertinib and crizotinib were administered concurrently for an epidermal growth factor receptor (EGFR)-mutated NSCLC developing a MET amplification as a resistance mechanism to osimertinib. Simultaneously, imatinib was administered for a metastatic gastrointestinal stromal tumor. The progression-free survival was 7 months for both tumors with this tritherapy. The use of therapeutic drug monitoring to assess plasma concentrations of each TKI was a powerful tool to manage the toxicity profile of this combination (creatine phosphokinase elevation) while preserving an optimal exposure to each TKI and treatment efficacy. We observed an imatinib over-exposition related to crizotinib introduction, probably explained by drug-drug interaction mediated by crizotinib enzymatic inhibition on cytochrome P-450 3A4. Posology adjustment due to therapeutic drug monitoring was probably involved in the good survival outcome of the patient. This tool should be used more routinely for patients treated by TKIs to prevent co-treatment interactions and, in particular, for patients receiving TKI combinations to obtain optimal therapeutic exposure and efficacy while reducing possible side-effects.

[Unusual association of BRAF and MEK inhibitors: Clinical response of metastatic melanoma treated with dabrafenib-cobimetinib]. / Association inhabituelle d'inhibiteurs de BRAF et de MEK : réponse clinique d'un mélanome métastatique traité par dabrafénib­cobimétinib.

Despite the efficacy of targeted therapies in melanoma, the management of adverse events with BRAFi and MEKi (inhibitors) is one of the limits of these treatments. Close monitoring is required to ensure efficacy and patient safety. In this case study, we report a patient treated for metastatic melanoma with an unusual and innovative combination of dabrafenib (BRAFi) and cobimetinib (MEKi), to manage pyrexia, and lead to complete remission for 19 months. This is the first case ever reported of metastatic melanoma treated with this off-label combination and characterized by the use of therapeutic drug monitoring.

Pharmacokinetic Variability Drives Palbociclib-Induced Neutropenia in Metastatic Breast Cancer Patients: Drug-Drug Interactions Are the Usual Suspects.

Palbociclib is a good candidate for therapeutic drug monitoring (TDM) due to its narrow therapeutic range and frequency of toxicities, particularly high-grade neutropenia. In this prospective, bicentric clinical trial, we evaluated the palbociclib exposure−toxicity relationship and determined the relevant sources of palbociclib pharmacokinetic variability, including drug−drug interactions (DDI). We followed 58 patients (mean age: 62.9 years) for 1 year. The geometric median of palbociclib plasma trough concentration (Ctrough) was 74.1 ng/mL. Neutropenia occurred in 70.7% of patients (high grade in 67.2% of patients). High-grade neutropenia occurrence during the first two palbociclib cycles was higher in patients with lower neutrophil count at initiation (p = 0.002). Palbociclib plasma Ctrough was correlated with high-grade neutropenia occurrence during the first two cycles (p = 0.024, OR 5.51). Co-treatment with agents that may interfere with palbociclib PK significantly influenced palbociclib Ctrough (p < 0.05). CYP3A4/P-glycoprotein inhibitors increased by 25% palbociclib Ctrough (p = 0.035), while antacids reduced it by 20% (p = 0.036). However, DDI did not have any significant effect on high-grade neutropenia occurrence (p > 0.05). This study confirms the major role of TDM to manage palbociclib safe use from the first week of treatment, particularly the significant incidence of hematological toxicity. Moreover, this first dedicated prospective study confirmed the importance of characterizing co-treatments to limit the DDI risk with oral-targeted therapies.

Impact of pharmacist consultation at clinical trial inclusion: an effective way to reduce drug-drug interactions with oral targeted therapy.

PURPOSE: Pharmacist consultation is unfrequently performed in oncology clinical trials that include patients who often have many co-treatments increasing the risk of drug-drug interactions (DDI). The aim of this study was to determine whether best possible medication history (BPMH) by hospital pharmacist at inclusion and therapeutic drug monitoring could be used for DDI risk evaluation and for current oral targeted therapy management. METHODS: A prospective clinical trial (ALCINA 2, NCT04025541) was carried out in metastatic breast cancer cohort treated by palbociclib to conduct pharmacokinetics-toxicity correlation study. BPMH was prospectively performed by the hospital pharmacist at each trial inclusion, followed by a contact to the patient's community pharmacy to complete the collected data. Pharmacokinetic analysis was performed on blood samples collected at day 15 of cycle 1 of palbociclib treatment. RESULTS: Pharmacist interventions indicated that at inclusion, current medications were incomplete for 63% of the enrolled patients (32/51). It allowed the real-time management of high-risk DDI detected in third of patients. The palbociclib Ctrough geometric median (min-max) was significantly higher in cohort with potential DDI [106 ng/mL (66.7-113)], than cohort without potential DDI [70.1 ng/mL (54.1-89.7)], p = 0.0284. CONCLUSION: This is the first prospective study evaluating the relevance of proactive BPMH by pharmacist with contact to the community pharmacy during the inclusion step of a clinical trial to ensure the efficacy and safety of the investigated drug. This investigation was thus able to highlight the statistically significant impact of these DDI on palbociclib plasma concentration variation during the clinical trial. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT04025541.

PXR Modulates the Prostate Cancer Cell Response to Afatinib by Regulating the Expression of the Monocarboxylate Transporter SLC16A1.

Resistance to castration is a crucial issue in the treatment of metastatic prostate cancer. Kinase inhibitors (KIs) have been tested as potential alternatives, but none of them are approved yet. KIs are subject of extensive metabolism at both the hepatic and the tumor level. Here, we studied the role of PXR (Pregnane X Receptor), a master regulator of metabolism, in the resistance to KIs in a prostate cancer setting. We confirmed that PXR is expressed in prostate tumors and is more frequently detected in advanced forms of the disease. We showed that stable expression of PXR in 22Rv1 prostate cancer cells conferred a resistance to dasatinib and a higher sensitivity to erlotinib, dabrafenib, and afatinib. Higher sensitivity to afatinib was due to a ~ 2-fold increase in its intracellular accumulation and involved the SLC16A1 transporter as its pharmacological inhibition by BAY-8002 suppressed sensitization of 22Rv1 cells to afatinib and was accompanied with reduced intracellular concentration of the drug. We found that PXR could bind to the SLC16A1 promoter and induced its transcription in the presence of PXR agonists. Together, our results suggest that PXR could be a biomarker of response to kinase inhibitors in castration-resistant prostate cancers.

Therapeutic Bayesian monitoring of sunitinib in two patients with impaired absorption or elimination.

WHAT IS KNOWN AND OBJECTIVE: Sunitinib pharmacokinetics can be influenced by the physio-pathological conditions of individual patients. Therapeutic drug monitoring (TDM) helps to optimize efficacy and reduce the risk of adverse effects. We report on the use of Bayesian analysis to optimize sunitinib blood levels. CASE SUMMARY: We describe two patients with risk of sunitinib pharmacokinetic variability due to gastrectomy and ongoing haemodialysis, respectively. TDM and Bayesian estimation allowed maintaining their sunitinib pharmacokinetic profiles within the usual limits. WHAT IS NEW AND CONCLUSION: Our analysis showed that Bayesian analysis can be successfully applied for real-time TDM to optimize sunitinib blood levels in patients with major comorbidities.

Population pharmacokinetic model of irinotecan and its four main metabolites in patients treated with FOLFIRI or FOLFIRINOX regimen.

PURPOSE: The aim of the present study was to characterize the pharmacokinetics of irinotecan and its four main metabolites (SN-38, SN-38G, APC and NPC) in metastatic colorectal cancer patients treated with FOLFIRI and FOLFIRINOX regimens and to quantify and explain the inter-individual pharmacokinetic variability in this context. METHODS: A multicenter study including 109 metastatic colorectal cancer patients treated with FOLFIRI or FOLFIRINOX regimen, associated or not with a monoclonal antibody, was conducted. Concentrations of irinotecan and its four main metabolites were measured in 506 blood samples during the first cycle of treatment. Collected data were analyzed using the population approach. First, fixed and random effects models were selected using statistical and graphical methods; second, the impact of covariates on pharmacokinetic parameters was evaluated to explain the inter-individual variability in pharmacokinetic parameters. RESULTS: A seven-compartment model best described the pharmacokinetics of irinotecan and its four main metabolites. First-order rates were assigned to distribution, elimination, and metabolism processes, except for the transformation of irinotecan to NPC which was nonlinear. Addition of a direct conversion of NPC into SN-38 significantly improved the model. Co-administration of oxaliplatin significantly modified the distribution of SN-38. CONCLUSION: To our knowledge, the present model is the first to allow a simultaneous description of irinotecan pharmacokinetics and of its four main metabolites. Moreover, a direct conversion of NPC into SN-38 had never been described before in a population pharmacokinetic model of irinotecan. The model will be useful to develop pharmacokinetic-pharmacodynamic models relating SN-38 concentrations to efficacy and digestive toxicities. CLINICAL TRIALS REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT00559676.

Model-Based Quantification of Impact of Genetic Polymorphisms and Co-Medications on Pharmacokinetics of Tamoxifen and Six Metabolites in Breast Cancer.

Variations in clinical response to tamoxifen (TAM) may be related to polymorphic cytochromes P450 (CYPs) involved in forming its active metabolite endoxifen (ENDO). We developed a population pharmacokinetic (PopPK) model for tamoxifen and six metabolites to determine clinically relevant factors of ENDO exposure. Concentration-time data for TAM and 6 metabolites come from a prospective, multicenter, 3-year follow-up study of adjuvant TAM (20 mg/day) in patients with breast cancer, with plasma samples drawn every 6 months, and genotypes for 63 genetic polymorphisms (PHACS study, NCT01127295). Concentration data for TAM and 6 metabolites from 928 patients (n = 27,433 concentrations) were analyzed simultaneously with a 7-compartment PopPK model. CYP2D6 phenotype (poor metabolizer (PM), intermediate metabolizer (IM), normal metabolizer (NM), and ultra-rapid metabolizer (UM)), CYP3A4*22, CYP2C19*2, and CYP2B6*6 genotypes, concomitant CYP2D6 inhibitors, age, and body weight had a significant impact on TAM metabolism. Formation of ENDO from N-desmethyltamoxifen was decreased by 84% (relative standard error (RSE) = 14%) in PM patients and by 47% (RSE = 9%) in IM patients and increased in UM patients by 27% (RSE = 12%) compared with NM patients. Dose-adjustment simulations support an increase from 20 mg/day to 40 and 80 mg/day in IM patients and PM patients, respectively, to reach ENDO levels similar to those in NM patients. However, when considering Antiestrogenic Activity Score (AAS), a dose increase to 60 mg/day in PM patients seems sufficient. This PopPK model can be used as a tool to predict ENDO levels or AAS according to the patient's CYP2D6 phenotype for TAM dose adaptation.

Cancer Immunotherapy Dosing: A Pharmacokinetic/Pharmacodynamic Perspective.

Immune check-point inhibitors are drugs that are markedly different from other anticancer drugs because of their indirect mechanisms of antitumoral action and their apparently random effect in terms of efficacy and toxicity. This marked pharmacodynamics variability in patients calls for reconsidering to what extent approved dosing used in clinical practice are optimal or whether they should require efforts for customization in outlier patients. To better understand whether or not dosing could be an actionable item in oncology, in this review, preclinical and clinical development of immune checkpoint inhibitors are described, particularly from the angle of dose finding studies. Other issues in connection with dosing issues are developed, such as the flat dosing alternative, the putative role therapeutic drug monitoring could play, the rise of combinatorial strategies, and pharmaco-economic aspects.

Vancomycin Serum Concentration after 48 h of Administration: A 3-Years Survey in an Intensive Care Unit.

The present study assessed the proportion of intensive care unit (ICU) patients who had a vancomycin serum concentration between 20 and 25 mg/L after 24-48 h of intravenous vancomycin administration. From 2016 to 2018, adult ICU patients with vancomycin continuous infusion (CI) for any indication were included. The primary outcome was the proportion of patients with a first-available vancomycin serum concentration between 20-25 mg/L at 24 h (D2) or 48 h (D3). Of 3894 admitted ICU patients, 179 were included. A median loading dose of 15.6 (interquartile range (IQR) = (12.5-20.8) mg/kg) was given in 151/179 patients (84%). The median daily doses of vancomycin infusion for D1 and D2 were 2000 [(IQR (1600-2000)) and 2000 (IQR (2000-2500)) mg/d], respectively. The median duration of treatment was 4 (2-7) days. At D2 or D3, the median value of first serum vancomycin concentration was 19.8 (IQR (16.0-25.1)) with serum vancomycin concentration between 20-25 mg/L reported in 43 patients (24%). Time spent in the ICU before vancomycin initiation was the only risk factor of non-therapeutic concentration at D2 or D3. Acute kidney injury occurred significantly more when vancomycin concentration was supra therapeutic at D2 or D3. At D28, 44 (26%) patients had died. These results emphasize the need of appropriate loading dose and regular monitoring to improve vancomycin efficacy and avoid renal toxicity.

The Anti-Cancer Drug Dabrafenib Is a Potent Activator of the Human Pregnane X Receptor.

The human pregnane X receptor (hPXR) is activated by a large set of endogenous and exogenous compounds and plays a critical role in the control of detoxifying enzymes and transporters regulating liver and gastrointestinal drug metabolism and clearance. hPXR is also involved in both the development of multidrug resistance and enhanced cancer cells aggressiveness. Moreover, its unintentional activation by pharmaceutical drugs can mediate drug-drug interactions and cause severe adverse events. In that context, the potential of the anticancer BRAF inhibitor dabrafenib suspected to activate hPXR and the human constitutive androstane receptor (hCAR) has not been thoroughly investigated yet. Using different reporter cellular assays, we demonstrate that dabrafenib can activate hPXR as efficiently as its reference agonist SR12813, whereas it does not activate mouse or zebrafish PXR nor hCAR. We also showed that dabrafenib binds to recombinant hPXR, induces the expression of hPXR responsive genes in colon LS174T-hPXR cancer cells and human hepatocytes and finally increases the proliferation in LS174T-hPXR cells. Our study reveals that by using a panel of different cellular techniques it is possible to improve the assessment of hPXR agonist activity for new developed drugs.

Liquid chromatography-tandem mass spectrometric assay for the quantification of CDK4/6 inhibitors in human plasma in a clinical context of drug-drug interaction.

The CDK4/6 inhibitors palbociclib and ribociclib are kinase inhibitors used in association with hormonal therapy for the management of patients with metastatic breast cancer. Like most kinase inhibitors, therapeutic drug monitoring may be used for personalize their dosage. To this aim, we developed and validated a sensitive and specific HPLC-MS/MS method for palbociclib and ribociclib quantification in blood samples. We then quantified exposure to palbociclib (plasma trough concentration; Ctrough) in a real-life cohort of patients with locally invasive or metastatic breast cancer (n = 18) at day 15 of the first cycle of palbociclib treatment to characterize palbociclib concentration at steady state (Clinicaltrials.gov identifier NCT04025541, IdRCB n° 2018-A00064-51, 03/07/2018). The geometric mean (± standard deviation [min-max]) of palbociclib plasma Ctrough was 88.58 ng/mL (± 26.4 [46.5 ng/mL - 133 ng/mL]) at day 15. Some covariates, such as drug-drug interactions, could explain the concentration variations observed in our Caucasian cohort. These first results in real-life settings obtained with our HPLC-MS/MS method give important information on palbociclib monitoring and pharmacokinetic variability.

Pharmacogenetics and pharmacokinetics modeling of unexpected and extremely severe toxicities after sorafenib intake.

A 53-year-old woman with papillary thyroid cancer treated with 800 mg sorafenib therapy rapidly experienced grade 3 toxicities. Dosing was reduced in a step-wise manner with several treatment discontinuations down to 200 mg every 2 days but severe toxicities continued. Plasma drug monitoring showed high exposure, even at low dose. Dosing was then further reduced at 200 mg every 3 days and tolerance was finally acceptable (i.e., grade 1 toxicity) with stable disease upon RECIST imaging. Pharmacogenetic investigations showed polymorphisms affecting both UGT1A9 (UGT1A9-rs3832043) and nuclear receptor PXR (NR1I2-rs3814055, NR1I2-rs2472677 and NR1I2-rs10934498), possibly resulting in downregulation of liver metabolizing enzymes of sorafenib (i.e., CYP and UGT). Patient's clearance (0.48 l/h) estimated by Bayesian approach was consistently lower than usually described. This is the first time that, in addition to mutations affecting UGT1A9, genetic polymorphisms of NR1I2 have possibly been associated with both plasma overexposure and severe toxicities upon sorafenib intake.

Probing Quantum Criticality and Symmetry Breaking at the Microscopic Level.

We report on an experimental study of the Lipkin-Meshkov-Glick model of quantum spins interacting at infinite range in a transverse magnetic field, which exhibits a ferromagnetic phase transition in the thermodynamic limit. We use dysprosium atoms of electronic spin J=8, subjected to a quadratic Zeeman light shift, to simulate 2J=16 interacting spins 1/2. We probe the system microscopically using single magnetic sublevel resolution, giving access to the spin projection parity, which is the collective observable characterizing the underlying Z_{2} symmetry. We measure the thermodynamic properties and dynamical response of the system, and we study the quantum critical behavior around the transition point. In the ferromagnetic phase, we achieve coherent tunneling between symmetry-broken states, and we test the link between symmetry breaking and the appearance of a finite order parameter.

Persistent response to vemurafenib in metastatic ameloblastoma with BRAF mutation: a case report.

BACKGROUND: Ameloblastomas are uncommon locally aggressive tumors of odontogenic epithelium that rarely metastasize. Currently, there is no standard of care for the metastatic forms. Several studies have shown that ameloblastomas frequently have a BRAF mutation. CASE PRESENTATION: We report a case of a 33-year-old Caucasian woman with ameloblastoma diagnosed 30 years ago who developed lung metastasis 19 years ago. Systemic oral treatment with vemurafenib, a BRAF inhibitor, was initiated 28 months ago within the AcSé French basket clinical trial of vemurafenib. CONCLUSIONS: The patient has shown a durable clinical, functional, and radiographic partial response with vemurafenib. These observations suggest the possibility of introducing neoadjuvant and/or adjuvant targeted therapy in locally advanced ameloblastoma to improve outcome. BRAF inhibition has proved to be an efficient strategy in patients with a BRAF-mutated ameloblastoma.

Enhanced Magnetic Sensitivity with Non-Gaussian Quantum Fluctuations.

The precision of a quantum sensor can overcome its classical counterpart when its constituents are entangled. In Gaussian squeezed states, quantum correlations lead to a reduction of the quantum projection noise below the shot noise limit. However, the most sensitive states involve complex non-Gaussian quantum fluctuations, making the required measurement protocol challenging. Here we measure the sensitivity of nonclassical states of the electronic spin J=8 of dysprosium atoms, created using light-induced nonlinear spin coupling. Magnetic sublevel resolution enables us to reach the optimal sensitivity of non-Gaussian (oversqueezed) states, well above the capability of squeezed states and about half the Heisenberg limit.

Toxicity and pharmacokinetic profile of SGM-101, a fluorescent anti-CEA chimeric antibody for fluorescence imaging of tumors in patients.

The real-time improvement of the intraoperative discrimination between different tissue types (particularly between tumor and adjacent normal tissue) using intraoperative imaging represents a considerable advance for oncology surgeons. However, the development of imaging agents is much slower than that of drug therapies, although surgery represents one of the few curative treatments for many solid tumors. SGM-101 is a recently described, innovative antibody conjugate in which the near-infrared fluorochrome BM-104 is covalently linked to a chimeric monoclonal antibody against carcinoembryonic antigen (CEA). SGM-101 was developed with the goal of providing oncology surgeons with an intraoperative imaging tool that allows the visualization of CEA-overexpressing tumors. This antigen is overexpressed in a wide range of human carcinomas, such as colorectal, gastric, pancreatic, non-small cell lung and breast carcinomas. Here we characterized SGM-101 safety prior to its clinical testing for real-time cancer mapping by oncology surgeons. Safety pharmacology and toxicology studies were performed after intravenous injection of SGM-101 in Wistar rats and in Beagle dogs. SGM-101 metabolism and pharmacokinetics were analyzed in rats and mice. Finally, the potential toxicity of the BM-104 dye and SGM-101 cross-reactivity were assessed in a panel of 42 human tissues. Our pre-clinical toxicology, pharmacology and pharmacokinetic results demonstrated the absence of significant adverse effects of both SGM-101 and BM-104 at doses well above the anticipated maximal human exposure. Taken together, the results of the pharmacology, pharmacokinetic and toxicology studies support the development of SGM-101 as a potentially useful and safe tumor-specific imaging tool that might improve the complete tumor resection rate.

Factors Affecting Tamoxifen Metabolism in Patients With Breast Cancer: Preliminary Results of the French PHACS Study.

In addition to the effect of cytochrome P450 (CYP) 2D6 genetic polymorphisms, the metabolism of tamoxifen may be impacted by other factors with possible consequences on therapeutic outcome (efficacy and toxicity). This analysis focused on the pharmacokinetic (PK)-pharmacogenetic evaluation of tamoxifen in 730 patients with adjuvant breast cancer included in a prospective multicenter study. Plasma concentrations of tamoxifen and six major metabolites, the genotype for 63 single-nucleotide polymorphisms, and comedications were obtained 6 months after treatment initiation. Plasma concentrations of endoxifen were significantly associated with CYP2D6 diplotype (P < 0.0001), CYP3A4*22 genotype (P = 0.0003), and concomitant intake of potent CYP2D6 inhibitors (P < 0.001). Comparison of endoxifen levels showed that the CYP2D6 phenotype classification could be improved by grouping intermediate metabolizer (IM)/IM and IM/poor metabolizer diplotype into IM phenotype for future use in tamoxifen therapy optimization. Finally, the multivariable regression analysis showed that formation of tamoxifen metabolites was independently impacted by CYP2D6 diplotype and CYP3A4*22, CYP2C19*2, and CYP2B6*6 genetic polymorphisms.

Quantum-enhanced sensing using non-classical spin states of a highly magnetic atom.

Coherent superposition states of a mesoscopic quantum object play a major role in our understanding of the quantum to classical boundary, as well as in quantum-enhanced metrology and computing. However, their practical realization and manipulation remains challenging, requiring a high degree of control of the system and its coupling to the environment. Here, we use dysprosium atoms-the most magnetic element in its ground state-to realize coherent superpositions between electronic spin states of opposite orientation, with a mesoscopic spin size J = 8. We drive coherent spin states to quantum superpositions using non-linear light-spin interactions, observing a series of collapses and revivals of quantum coherence. These states feature highly non-classical behavior, with a sensitivity to magnetic fields enhanced by a factor 13.9(1.1) compared to coherent spin states-close to the Heisenberg limit 2J = 16-and an intrinsic fragility to environmental noise.