ADCT-602, a Novel PBD Dimer-containing Antibody-Drug Conjugate for Treating CD22-positive Hematologic Malignancies.

Relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) and lymphomas have poor patient outcomes; novel therapies are needed. CD22 is an attractive target for antibody-drug conjugates (ADCs), being highly expressed in R/R B-ALL with rapid internalization kinetics. ADCT-602 is a novel CD22-targeting ADC, consisting of humanized mAb hLL2-C220, site specifically conjugated to the pyrrolobenzodiazepine dimer-based payload tesirine. In preclinical studies, ADCT-602 demonstrated potent, specific cytotoxicity in CD22-positive lymphomas and leukemias. ADCT-602 was specifically bound, internalized, and trafficked to lysosomes in CD22-positive tumor cells; after cytotoxin release, DNA interstrand crosslink formation persisted for 48 hours. In the presence of CD22-positive tumor cells, ADCT-602 caused bystander killing of CD22-negative tumor cells. A single ADCT-602 dose led to potent, dose-dependent, in vivo antitumor activity in subcutaneous and disseminated human lymphoma/leukemia models. Pharmacokinetic analyses (rat and cynomolgus monkey) showed excellent stability and tolerability of ADCT-602. Cynomolgus monkey B cells were efficiently depleted from circulation after one dose. Gene signature association analysis revealed IRAK1 as a potential marker for ADCT-602 resistance. Combining ADCT-602 + pacritinib was beneficial in ADCT-602-resistant cells. Chidamide increased CD22 expression on B-cell tumor surfaces, increasing ADCT-602 activity. These data support clinical testing of ADCT-602 in R/R B-ALL (NCT03698552) and CD22-positive hematologic cancers.

The Role of Specific ATP-Binding Cassette Transporters in the Acquired Resistance to Pyrrolobenzodiazepine Dimer-Containing Antibody-Drug Conjugates.

Antibody-drug conjugates (ADC) containing pyrrolobenzodiazepine (PBD) dimers are being evaluated clinically in both hematologic and solid tumors. These include ADCT-301 (camidanlumab tesirine) and ADCT-402 (loncastuximab tesirine) in pivotal phase II trials that contain the payload tesirine, which releases the PBD dimer warhead SG3199. An important consideration in future clinical development is acquired resistance. The aim was to generate and characterize PBD acquired resistant cell lines in both hematologic and solid tumor settings. Human Karpas-299 (ALCL) and NCI-N87 (gastric cancer) cells were incubated with increasing IC50 doses of ADC (targeting CD25 and HER2, respectively) or SG3199 in a pulsed manner until stable acquired resistance was established. The level of resistance achieved was approximately 3,000-fold for ADCT-301 and 3-fold for SG3199 in Karpas-299, and 8-fold for ADCT-502 and 4-fold for SG3199 in NCI-N87. Cross-resistance between ADC and SG3199, and with an alternative PBD-containing ADC or PBD dimer was observed. The acquired resistant lines produced fewer DNA interstrand cross-links, indicating an upstream mechanism of resistance. Loss of antibody binding or internalization was not observed. A human drug transporter PCR Array revealed several genes upregulated in all the resistant cell lines, including ABCG2 and ABCC2, but not ABCB1(MDR1). These findings were confirmed by RT-PCR and Western blot, and inhibitors and siRNA knockdown of ABCG2 and ABCC2 recovered drug sensitivity. These data show that acquired resistance to PBD-ADCs and SG3199 can involve specific ATP-binding cassette drug transporters. This has clinical implications as potential biomarkers of resistance and for the rational design of drug combinations.

Antitumor Activity of MEDI3726 (ADCT-401), a Pyrrolobenzodiazepine Antibody-Drug Conjugate Targeting PSMA, in Preclinical Models of Prostate Cancer.

Prostate-specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase that is highly expressed in nearly all prostate cancers with the highest expression in metastatic castration-resistant prostate cancer (mCRPC). The prevalence of increased surface expression and constitutive internalization of PSMA make it an attractive target for an antibody-drug conjugate (ADC) approach to treating patients with mCRPC. MEDI3726 (previously known as ADCT-401) is an ADC consisting of an engineered version of the anti-PSMA antibody J591 site specifically conjugated to the pyrrolobenzodiazepine (PBD) dimer tesirine. MEDI3726 specifically binds the extracellular domain of PSMA and, once internalized, releases the PBD dimer to crosslink DNA and trigger cell death. In vitro, MEDI3726 demonstrated potent and specific cytotoxicity in a panel of PSMA-positive prostate cancer cell lines, consistent with internalization and DNA interstrand crosslinking. In vivo, MEDI3726 showed robust antitumor activity against the LNCaP and the castration-resistant CWR22Rv1 prostate cancer cell line xenografts. MEDI3726 also demonstrated durable antitumor activity in the PSMA-positive human prostate cancer patient-derived xenograft (PDX) LuCaP models. This activity correlated with increased phosphorylated Histone H2AX in tumor xenografts treated with MEDI3726. MEDI3726 is being evaluated in a phase I clinical trial as a treatment for patients with metastatic castrate-resistant prostate cancer (NCT02991911). Mol Cancer Ther; 17(10); 2176-86. ©2018 AACR.

Screening for Atrial Fibrillation Using Economical and Accurate Technology (From the SAFETY Study).

The prevalence of atrial fibrillation (AF) is estimated at more than 3% in the adult population and there has been increased interest in screening for AF. In the SAFETY trial we chose to evaluate if inexpensive, wearable, consumer electrocardiography (ECG) sensing devices (Polar-H7 [PH7] and Firstbeat Bodyguard 2 [BG2]), could be used to detect AF accurately. We undertook a case-control study of 418 participants aged >65 (82 with AF and/or flutter at the study visit and 336 without) attending 3 general practice surgeries in Hampshire, UK for a single screening visit. The PH7 and BG2 devices were tested alongside 2 established AF detection devices (AliveCor and WatchBP) in random order and the diagnosis of AF was confirmed by 12-Lead ECG interpreted by a panel of cardiologists. The sensitivity (95% confidence interval [CI] range), specificity (95% CI range), and overall accuracy (95% CI range) of the 4 devices were: AliveCor: 87.8% (78.7% to 94.0%), 98.8% (97.0% to 99.7%), 96.7% (94.4% to 98.2%); WatchBP: 96.3% (89.7% to 99.2%), 93.5% (90.3% to 95.9%), 94.0% (91.3% to 96.1%): PH7: 96.3% (89.7% to 99.2%), 98.2% (96.2% to 99.3%), 97.9% (96.0% to 99.0%). BG2: 96.3% (89.7% to 99.2%), 98.5% (96.6% to 99.5%), 98.1% (96.3% to 99.2%). The PH7 and BG2 devices were highly reliable (the devices acquired sufficient data and obtained a diagnostic result in all but 1 participant on the first attempt). In conclusion, inexpensive, consumer heart rate monitoring devices (PH7 and BG2) can be used to detect AF accurately with sensitivity and specificity >95%. The consumer devices performed as well or better than WatchBP and AliveCor and have the capability to store or transmit ECG data which could be used to confirm AF.

Pre-clinical pharmacology and mechanism of action of SG3199, the pyrrolobenzodiazepine (PBD) dimer warhead component of antibody-drug conjugate (ADC) payload tesirine.

Synthetic pyrrolobenzodiazepine (PBD) dimers, where two PBD monomers are linked through their aromatic A-ring phenolic C8-positions via a flexible propyldioxy tether, are highly efficient DNA minor groove cross-linking agents with potent cytotoxicity. PBD dimer SG3199 is the released warhead component of the antibody-drug conjugate (ADC) payload tesirine (SG3249), currently being evaluated in several ADC clinical trials. SG3199 was potently cytotoxic against a panel of human solid tumour and haematological cancer cell lines with a mean GI50 of 151.5 pM. Cells defective in DNA repair protein ERCC1 or homologous recombination repair showed increased sensitivity to SG3199 and the drug was only moderately susceptible to multidrug resistance mechanisms. SG3199 was highly efficient at producing DNA interstrand cross-links in naked linear plasmid DNA and dose-dependent cross-linking was observed in cells. Cross-links formed rapidly in cells and persisted over 36 hours. Following intravenous (iv) administration to rats SG3199 showed a very rapid clearance with a half life as short as 8 minutes. These combined properties of cytotoxic potency, rapid formation and persistence of DNA interstrand cross-links and very short half-life contribute to the emerging success of SG3199 as a warhead in clinical stage ADCs.

ADCT-402, a PBD dimer-containing antibody drug conjugate targeting CD19-expressing malignancies.

Human CD19 antigen is a 95-kDa type I membrane glycoprotein in the immunoglobulin superfamily whose expression is limited to the various stages of B-cell development and differentiation and is maintained in the majority of B-cell malignancies, including leukemias and non-Hodgkin lymphomas of B-cell origin. Coupled with its differential and favorable expression profile, CD19 has rapid internalization kinetics and is not shed into the circulation, making it an ideal target for the development of antibody-drug conjugates (ADCs) to treat B-cell malignancies. ADCT-402 (loncastuximab tesirine) is a novel CD19-targeted ADC delivering SG3199, a highly cytotoxic DNA minor groove interstrand crosslinking pyrrolobenzodiazepine (PDB) dimer warhead. It showed potent and highly targeted in vitro cytotoxicity in CD19-expressing human cell lines. ADCT-402 was specifically bound, internalized, and trafficked to lysosomes in CD19-expressing cells and, following release of the PBD warhead, resulted in formation of DNA crosslinks that persisted for 36 hours. Bystander killing of CD19- cells by ADCT-402 was also observed. In vivo, single doses of ADCT-402 resulted in highly potent, dose-dependent antitumor activity in several subcutaneous and disseminated human tumor models with marked superiority to comparator ADCs delivering tubulin inhibitors. Dose-dependent DNA crosslinks and γ-H2AX DNA damage response were measured in tumors by 24 hours after single dose administration, whereas matched peripheral blood mononuclear cells showed no evidence of DNA damage. Pharmacokinetic analysis in rat and cynomolgus monkey showed excellent stability and tolerability of ADCT-402 in vivo. Together, these impressive data were used to support the clinical testing of this novel ADC in patients with CD19-expressing B-cell malignancies.

Synthesis and in vitro evaluation of SG3227, a pyrrolobenzodiazepine dimer antibody-drug conjugate payload based on sibiromycin.

A novel pyrrolobenzodiazepine dimer payload, SG3227, was rationally designed based on the naturally occurring antitumour compound sibiromycin. SG3227 was synthesized from a dimeric core in an efficient fashion. An unexpected room temperature Diels-Alder reaction occurred during the final step of the synthesis and was circumvented by use of an iodoacetamide conjugation moiety in place of a maleimide. The payload was successfully conjugated to trastuzumab and the resulting ADC exhibited potent activity against a HER2-expressing human cancer cell line in vitro.

Design and Synthesis of Tesirine, a Clinical Antibody-Drug Conjugate Pyrrolobenzodiazepine Dimer Payload.

Pyrrolobenzodiazepine dimers are an emerging class of warhead in the field of antibody-drug conjugates (ADCs). Tesirine (SG3249) was designed to combine potent antitumor activity with desirable physicochemical properties such as favorable hydrophobicity and improved conjugation characteristics. One of the reactive imines was capped with a cathepsin B-cleavable valine-alanine linker. A robust synthetic route was developed to allow the production of tesirine on clinical scale, employing a flexible, convergent strategy. Tesirine was evaluated in vitro both in stochastic and engineered ADC constructs and was confirmed as a potent and versatile payload. The conjugation of tesirine to anti-DLL3 rovalpituzumab has resulted in rovalpituzumab-tesirine (Rova-T), currently under evaluation for the treatment of small cell lung cancer.

Does routine pressure wire assessment influence management strategy at coronary angiography for diagnosis of chest pain?: the RIPCORD study.

BACKGROUND: The use of coronary angiography (CA) for diagnosis and management of chest pain (CP) has several flaws. The assessment of coronary artery disease using fractional flow reserve (FFR) is a well-validated technique for describing lesion-level ischemia and improves clinical outcome in the context of percutaneous coronary intervention. The impact of routine FFR at the time of diagnostic CA on patient management has not been determined. METHODS AND RESULTS: Two hundred patients with stable CP underwent CA for clinical indications. The supervising cardiologist (S.C.) made a management plan based on CA (optimal medical therapy alone, percutaneous coronary intervention, coronary artery bypass grafting, or more information required) and also recorded which stenoses were significant. An interventional cardiologist then measured FFR in all patent coronary arteries of stentable diameter (≥2.25 mm). S.C. was then asked to make a second management plan when FFR results were disclosed. Overall, after disclosure of FFR data, management plan based on CA alone was changed in 26% of patients, and the number and localization of functional stenoses changed in 32%. Specifically, of 72 cases in which optimal medical therapy was recommended after CA, 9 (13%) were actually referred for revascularization with FFR data. By contrast, of 89 cases in whom management plan was optimal medical therapy based on FFR, revascularization would have been recommended in 25 (28%) based on CA. CONCLUSIONS: Routine measurement of FFR at CA has important influence both on which coronary arteries have significant stenoses and on patient management. These findings could have important implications for clinical practice. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrial.gov. Unique identifier: NCT01070771.

Effect of clopidogrel withdrawal on platelet reactivity and vascular inflammatory biomarkers 1 year after drug-eluting stent implantation: results of the prospective, single-centre CESSATION study.

BACKGROUND: The optimal duration of clopidogrel treatment, particularly following drug-eluting stent (DES) implantation, remains contentious. Previous studies have observed a clustering of adverse events following clopidogrel cessation 1 year after DES, the aetiology of which is poorly understood. OBJECTIVE: To investigate, in the prospective CESSATION study, the effect of clopidogrel withdrawal at 1 year after DES implantation on (i) arachidonic acid (AA)- and adenosine diphosphate (ADP)-induced platelet aggregation, and (ii) biomarkers of vascular inflammation, including soluble CD40 ligand (sCD40L), high-sensitivity C-reactive protein (hsCRP) and interleukin 6 (IL-6). METHODS AND RESULTS: The prospective CESSATION study was undertaken in 33 patients receiving aspirin and due to discontinue clopidogrel 1 year after DES. Platetet reactivity was measured using short thromboelastography, and compliance with aspirin determined from serum thromboxane B(2) (TXB(2)) levels. Venesection was performed at 4 weeks and 24 h before, and at 24 h, 48 h, 1, 2 and 4 weeks after, clopidogrel cessation. Following clopidogrel withdrawal, there was (i) a predictable increase in ADP-induced platelet aggregation (ii) an unexpected significant increase in AA-induced platelet aggregation (iii) a decline in IL-6 and hsCRP at 1 week and 4 weeks respectively; and (iv) a non-significant increase in sCD40L at 4 weeks TXB(2) levels were consistently suppressed, indicating complete inhibition of cyclo-oxygenase-1 by aspirin. CONCLUSION: An aspirin-independent, time-dependent increase in AA-induced platelet activation following clopidogrel withdrawal in patients with a DES has been described. New insights into a potential mechanism for the observed clustering of adverse events that occur early after clopidogrel cessation have been provided. These findings raise the question as to whether AA-induced clotting is an appropriate test of aspirin sensitivity.

Comparable clinical outcomes with paclitaxel- and sirolimus-eluting stents in unrestricted contemporary practice.

OBJECTIVES: This study was designed to compare the outcomes of paclitaxel-eluting stents (PES) and sirolimus-eluting stents (SES) in a contemporaneous cohort of real-world patients. BACKGROUND: A number of randomized comparisons of PES and SES have shown unequivocal advantages for SES in angiographic end points such as late loss. However, the data on clinical outcomes are less consistent. METHODS: All consecutive patients successfully treated with only SES or PES in de novo native vessel lesions between March 2003 and March 2005 were analyzed. Our end points were major adverse cardiac events (MACE), a composite of death, myocardial infarction (MI), target vessel revascularization (TVR), and target lesion revascularization (TLR). We also analyzed late loss and angiographic restenosis. RESULTS: There were 609 patients (1,064 lesions) treated with PES and 674 patients (1,205 lesions) treated with SES. Diabetes mellitus was present in 26.8% of patients and multivessel disease in 75% of patients. Bifurcations made up 16.3% of lesions, chronic occlusions 9.5%, left main 4.8%, and American Heart Association/American College of Cardiology type B2/C 75.4%. Despite a higher late loss in the PES group (p = 0.0001), there were no differences in angiographic restenosis (PES 18% vs. SES 17.8%, p = 0.95), TLR (PES 11.9% vs. SES 11%, p = 0.47), or MACE (PES 21.3% vs. SES 21.1%, p = 0.95). The relative risk of MACE for the PES group was 1.02 (95% confidence interval [CI] 0.78 to 1.33). Multivariable analysis confirmed the lack of association of stent type with MACE (odds ratio 1.03 [95% CI 0.77 to 1.38], p = 0.83) and TLR (odds ratio 1.08 [95% CI 0.81 to 1.44], p = 0.61). CONCLUSIONS: In this complex cohort, both stent platforms demonstrated similar clinical outcomes despite different late loss.

Recanalization of an occluded right coronary artery into the right internal mammary artery using a retrograde approach.

Recanalization of chronic total occlusions (CTO) remains one of the most technically challenging areas in interventional cardiology. We report a case of retrograde recanalization of a chronically occluded mid-right coronary artery into a right internal mammary graft via a septal collateral. This retrograde approach provides another option for CTO recanalization when the anterograde approach has failed.

Percutaneous coronary intervention in patients with a single remaining vessel.

Percutaneous coronary intervention in a patient's last remaining coronary conduit is perceived to be high risk, although there are no published data on outcomes in this lesion cohort. We report our experience with 16 patients who underwent intervention in their sole remaining vessel between 1998 and 2005. All patients had previously undergone coronary artery bypass grafting, had a history of myocardial infarction, had impaired left ventricular systolic function, and were symptomatic with unstable angina or minimal effort angina. There was 1 periprocedural death 10 hours after the procedure, and another patient died 4 months after the procedure. At 6-month follow-up, 2 patients had undergone target lesion revascularization. There was a significant and sustained improvement in symptom status, with 75% of patients being asymptomatic or in Canadian Cardiovascular Society class I after 6 months. Given the complexity of the patients and lesions treated in this cohort, periprocedural and long-term outcomes are acceptable with a notable improvement in symptomatic status. In conclusion, these data support percutaneous intervention as a realistic treatment option for this often highly symptomatic and difficult-to-treat patient cohort.