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Spinal muscular atrophy (SMA) is a rare, genetic neurodegenerative disorder caused by insufficient production of survival motor neuron (SMN) protein. Diminished SMN protein levels lead to motor neuron loss, causing muscle atrophy and weakness that impairs daily functioning and reduces quality of life. SMN upregulators offer clinical improvements and increased survival in SMA patients, although significant unmet needs remain. Myostatin, a TGF-β superfamily signaling molecule that binds to the activin II receptor, negatively regulates muscle growth; myostatin inhibition is a promising therapeutic strategy for enhancing muscle. Combining myostatin inhibition with SMN upregulation, a comprehensive therapeutic strategy targeting the whole motor unit, offers promise in SMA. Taldefgrobep alfa is a novel, fully human recombinant protein that selectively binds to myostatin and competitively inhibits other ligands that signal through the activin II receptor. Given a robust scientific and clinical rationale and the favorable safety profile of taldefgrobep in patients with neuromuscular disease, the RESILIENT phase 3, randomized, placebo-controlled trial is investigating taldefgrobep as an adjunct to SMN upregulators in SMA (NCT05337553). This manuscript reviews the role of myostatin in muscle, explores the preclinical and clinical development of taldefgrobep and introduces the phase 3 RESILIENT trial of taldefgrobep in SMA.

Antisense oligonucleotides (ASOs) bind sequence specifically to the target RNA and modulate protein expression through several different mechanisms. The ASO field is an emerging area of drug development that targets the disease source at the RNA level and offers a promising alternative to therapies targeting downstream processes. To translate ASO-based therapies into a clinical success, it is crucial to overcome the challenges associated with off-target side effects and insufficient biological activity. In this regard, several chemical modifications and diverse delivery strategies have been explored. In this review, we systematically discuss the chemical modifications, mechanism of action, and optimized delivery strategies of several different classes of ASOs. Further, we highlight the recent advances made in development of ASO-based drugs with a focus on drugs that are approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for clinical applications. We also discuss various promising ASO-based drug candidates in the clinical trials, and the outstanding opportunity of emerging microRNA as a viable therapeutic target for future ASO-based therapies.

State of the art minimally invasive treatments and diagnostics of neurological and cardiovascular diseases demand for flexible instruments and implants that enable sensing and stimulation of bioelectric signals. Besides medical applications, implantable bioelectronic brain-computer interfaces are envisioned as the next step in communication and data transfer. Conventional microelectrode arrays used for these types of applications are based on polymer substrates that are not suitable for biostable, rigid and self-expanding devices. Here, we present fully integrated bioelectrodes on superelastic NiTi carriers fabricated by microsystem technology processes. The insulation between the metallic NiTi structure and the Pt electrode layer is realized by different oxide layers (SiO x , TaO x and Yttrium stabilized Zirconia YSZ). Key properties of bioelectronic implants such as dissolution in body fluids, biocompatibility, mechanical properties and bioelectrical sensing/stimulation capabilities have been investigated by in vitro methods. Particular devices with YSZ are biostable and biocompatible, enabling sensing and stimulation. The major advantage of this system is the combination of medically approved materials and novel fabrication technology that enables miniaturization and integration beyond the state-of-the-art processes. The results demonstrate that this functionalization of superelastic NiTi is an enabling technology for the development of new kinds of bioelectronic devices., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Acquandas GmbH is a Kiel based company and OEM supplier for medical and industrial components. Components include flexible devices for bioelectronics sensing or stimulation and other microtechnological parts., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Progressive supranuclear palsy is a rare neurodegenerative disease associated with dysfunctional tau protein. BIIB092 is a humanised monoclonal antibody that binds to N-terminal tau and is thus being assessed as a potential novel treatment for progressive supranuclear palsy. We aimed to investigate the safety and tolerability of BIIB092 in individuals with progressive supranuclear palsy., Methods: This 12-week, double-blind, randomised, placebo-controlled, multiple ascending dose, phase 1b trial was done at 13 outpatient sites in the USA. Participants aged 41-86 years with probable or possible progressive supranuclear palsy with a score of 20 or greater on the Mini-Mental State Examination (MMSE) were enrolled. Three BIIB092 dose escalation cohorts (150 mg, 700 mg, or 2100 mg; eight participants per cohort) were tested sequentially. For each dose cohort, the first two participants were randomly assigned by a computer-generated scheme to receive either BIIB092 or placebo intravenously every 4 weeks for 57 days. After 2 days, the six remaining participants in each cohort were randomly assigned (5:1) to receive BIIB092 or placebo for 57 days. An additional expansion panel of 24 patients was randomly assigned (3:1) to receive 2100 mg or placebo every 4 weeks for 57 days. All participants were followed up to day 85. The primary outcome was safety, which was analysed in the treated population (all enrolled participants who received at least one dose of the study drug). This trial is registered with ClinicalTrials.gov, NCT02460094., Findings: Between Oct 2, 2015, and Oct 19, 2016, 48 participants were enrolled and randomly assigned to the BIIB092 (n=36) and placebo (n=12) groups. No apparent demographic differences were observed between the two groups at baseline. All 48 participants completed the treatment phase of the study. Adverse events were generally mild to moderate in severity; the most common in the placebo and BIIB092 groups were falls (in two [17%] of 12 patients and in ten [28%] of 36 patients), urinary tract infections (in one [8%] of 12 and in six [17%] of 36), contusions (in one [8%] of 12 and in five [14%] of 36), and headaches (in none and in five [14%] of 36). Four serious adverse events resulting in admission to hospital were reported in three participants who received BIIB092 2100 mg: two severe adverse events of urinary tract infection, one severe adverse event of change in mental status, and one moderate adverse event of aspiration pneumonia. None was considered to be related to the study drug, all were resolved, and no deaths were reported., Interpretation: Repeated administration of the anti-tau monoclonal antibody BIIB092, at doses of up to 2100 mg, appears to be well tolerated in participants with progressive supranuclear palsy. Results of this phase 1b trial have informed the design of the ongoing phase 2 PASSPORT (NCT03068468) study to examine the efficacy and safety of BIIB092., Funding: Bristol-Myers Squibb, Biogen., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Introduction: Extracellular tau is hypothesized to mediate the onset and progression of tauopathies, including Alzheimer's disease, progressive supranuclear palsy, and a subset of frontotemporal lobar degenerations. A putative strategy for treating these disorders is to reduce extracellular tau levels using tau-directed immunotherapy. The results of the first-in-human study of BIIB092 (formerly BMS-986168/IPN007), a humanized monoclonal antibody that binds to N-terminal tau, are reported here. This randomized, double-blind, single ascending dose study evaluated the safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity profile of BIIB092 after a single intravenous infusion in healthy participants., Methods: Sixty-five participants were randomized to receive a single intravenous infusion of placebo or BIIB092 at doses of 21, 70, 210, 700, 2100, or 4200 mg (or 700 or 2100 mg for Japanese participants). Serial blood and cerebrospinal fluid samples were obtained for assessment of pharmacokinetic parameters and unbound N-terminal tau suppression., Results: There were no deaths, serious adverse events (AEs), severe AEs, or discontinuations due to an AE. The majority of AEs were mild. Serum BIIB092 concentrations increased in a dose-proportional manner and suppressed unbound cerebrospinal fluid N-terminal tau by 67%-97% at 28 days after dose, with doses of ≥210 mg producing persistent unbound N-terminal tau suppression over 12 weeks. Levels of cerebrospinal fluid N-terminal tau suppression were similar for Japanese and non-Japanese participants., Discussion: BIIB092 was generally safe and well tolerated after a single dose of up to 4200 mg, and up to 2100 mg in Japanese participants. BIIB092 exhibited a dose-dependent increase in the extent and duration of unbound N-terminal tau suppression.

This review describes the European Union and the US regulations applicable to food colours. Despite the different regulatory frameworks, the overall approach is similar, based on well-established risk-assessment procedures and risk-management measures. However, differences impacting free movement of goods can be found in the details and implementation of regulations. Using additives approved only in the US or in the EU implies that producers aiming to export need to adjust their product composition to the export market. Failure to comply may give rise to claims of adulteration, misbranding or non-compliance and rejection at the border or recall from the market. A careful comparison of the level of protection provided by the two sets of regulations, the criteria of good manufacturing practice (GMP) inspections and the certification requirements could be key to aligning the rules and to negotiating mutual recognition agreements. This review provides an extensive overview of the similarities and differences in regulating food colours in the EU and the US.

Self-expandable medical devices provide mechanical functionality at a specific location of the human body and are viable for minimal invasive procedures. Besides radiopaque markers and drug-eluting coatings, next generation self-expandable devices can be equipped with additional functionality, such as conductive and flexible electrodes, which enables chronic recording of bioelectrical signals, stimulating or ablating tissue. This promises new therapeutic options in various medical fields, among them in particular neuromodulation (e.g. deep brain stimulation), BioMEMS, radio frequency ablation, mapping or denervation. However, the fabrication of such multi-functional devices is challenging. For this study we have realized a 35 μm thick, superelastic NiTi thin film stent structure with six isolated electrodes on the outer circumference, each electrode connected to a contact pad at the end of the stent structure, using magnetron sputtering, UV lithography and wet chemical etching. Mechanical and electrical properties of the device during typical loading conditions, i.e. crimping, simulated pulsatile and electrochemical testing, were characterized and reveal promising results. For the fabrication of future multifunctional, minimal invasive medical devices, such as electroceuticals or other intelligent implants, NiTi thin film technology is therefore a versatile alternative to conventional fabrication routes.

The positive influence of crystallographic compatibility on the thermal transformation stability has been already investigated extensively in the literature. However, its influence on the stability of the shape memory effect or superelasticity used in actual applications is still unresolved. In this investigation sputtered films of a highly compatible TiNiCuCo composition with a transformation matrix middle eigenvalue of 1±0.01 are exposed to thermal as well as to superelastic cycling. In agreement with previous results the thermal transformation of this alloy is with a temperature shift of less than 0.1 K for 40 cycles very stable; on the other hand, superelastic degradation behaviour was found to depend strongly on heat treatment parameters. To reveal the transformation dissimilarities between the differently heat-treated samples, the microstructure has been analysed by transmission electron microscopy, in situ stress polarization microscopy and synchrotron analysis. It is found that good crystallographic stability is not a sufficient criterion to avoid defect generation which guarantees high superelastic stability. For the investigated alloy, a small grain size was identified as the determining factor which increases the yield strength of the composition and decreases the functional degradation during superelastic cycling.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'., (© 2016 The Author(s).)

Background: The aim of this study was to analyze risk factors promoting development of recoarctation (Re-CoA) in neonates who survived aortic arch repair from an anterior approach., Methods: Fifty consecutive neonates with biventricular morphology and ductal-dependent lower body perfusion who were discharged home following aortic arch repair with cardiopulmonary bypass between 2000 and 2012 were retrospectively reviewed. Arch anatomy was either interruption (n = 10) or hypoplasia with coarctation (n = 40). Aortic arch reconstruction was performed by using patch material (bovine pericardium, n = 30, homograft, n = 10, or glutaraldehyde-treated autologous pericardium, n = 7), and three patients underwent direct end-to-side anastomosis. Antegrade cerebral and continuous myocardial perfusion was performed in 39 and 21 patients, respectively. Kaplan-Meier freedom from Re-CoA was calculated. Morphologic and perioperative data indicating increased risk of Re-CoA by univariate analysis were included in multivariate Cox regression analysis., Results: Mean follow-up was 5.3 ± 4.1 years. Re-CoA occurred in 13 patients and was treated successfully by balloon dilatation (n = 6) or surgery (n = 7). Freedom from Re-CoA after 1 and 5 years was 83 ± 5 and 79 ± 6%, respectively. Two patients died early after surgical repair of Re-CoA. The use of autologous pericardium for aortic arch augmentation was the only independent risk factor for development of Re-CoA (hazard ratio: 4.3 [95% confidence interval: 1.2-16.1]; p = 0.028)., Conclusion: Re-CoA following neonatal aortic arch surgery can be treated by balloon dilatation or surgery, if adequate. In this study, the risk for development of Re-CoA was independently increased by the use of autologous pericardium during initial arch repair., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: Leaving an inter-atrial communication (IAC) open for left atrial decompression is often recommended in neonates with aortic arch obstruction undergoing primary repair. In this study, outcomes in these patients were compared to those with intact atrial septum after repair., Methods: Between 2000 and 2013, 53 consecutive neonates with severe aortic arch obstruction (hypoplasia: n = 45, interruption: n = 8) underwent primary repair from an anterior approach. Median age and weight were 8 days (range: 2-30) and 3.2 kg (range: 2.4-4.4), respectively. Cardiac morphology included a ventricular septal defect (VSD, large: n = 28, small: n = 7), malposition of great arteries (n = 10), and severe left ventricular outflow tract obstruction (LVOTO, n = 10). During corrective surgery IAC was closed (group-I, n = 37) or partially left-open (group-II, n = 16). Primary endpoints were hospital death, and re-intervention (surgery and/or balloon) due to aortic arch re-coarctation or recurrent LVOTO. Statistically significant variables by univariate analysis were incorporated in the corresponding multivariable regression model., Results: Regarding morphological discrepancies more patients in group-II presented with LVOTO (p = 0.05), or the combination of arch hypoplasia, intact ventricular septum and normal ventriculo-arterial connection (p = 0.017). Hospital mortality was 8.1% in group-I and 37.5% in group-II (p = 0.016). Re-intervention was performed in 13 patients (group-I: n = 6 vs. group-II: n = 7) due to aortic arch re-coarctation (n = 12) and/or recurrent LVOTO (n = 3), and resulted in a Kaplan-Meier freedom from re-intervention of 87 ± 6% and 79 ± 8% in group-I, and 64 ± 14% and 64 ± 14% in group-II after 1 and 5 years, respectively (p = 0.016). Multivariate analysis revealed LVOTO as an independent risk factor for hospital death (p = 0.042), whereas both LVOTO and left-open IAC (p = 0.001 and 0.01) were independent risk factors for re-intervention., Conclusions: A left-open IAC increases risk of re-intervention at the left heart aorta complex. Sustained left-to-right shunting on atrial level seems to induce preload reduction of the often restrictive left ventricle leading to decreased aortic blood flow.

Background: A number of recent reports have described novel failure mechanisms of metal-on-metal bearings in total and resurfacing hip arthroplasty. Hip arthroplasties with metal-on-metal articulations are also subject to the traditional methods of failure seen with different bearing couples. There is currently little information in the literature to help guide timely clinical evaluation and management of these patients., Questions/purposes: We therefore describe the (1) clinical presentations; (2) reasons for failure; (3) operative findings; and (4) histologic findings in patients with failed metal-on-metal hip arthroplasties., Methods: We retrospectively identified all 37 patients (37 hips) with metal on metal total hip or resurfacing arthroplasties who underwent revision over the past 3 years at our institution. Relevant clinical, radiographic, laboratory, intraoperative, and histopathologic findings were analyzed for all patients., Results: Of the 37 patients, 10 were revised for presumed hypersensitivity specific to the metal-on-metal articulation. This group included eight patients with tissue histology confirming chronic inflammation with lymphocytic infiltration, eight with aseptic loosening of a monoblock screwless uncemented acetabular component, two with iliopsoas impingement associated with a large-diameter femoral head, and three with femoral neck fracture after resurfacing arthroplasty; the remainder of the patients were revised for infection, instability, component malposition, and periprosthetic fracture., Conclusions: Increased awareness of the modes of failure will bring to light the potential complications particular to metal-on-metal articulations while placing these complications into the context of failures associated with all hip arthroplasties. This novel clinical information should be valuable for the practicing surgeon faced with this patient population., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Gas turbines and other large industrial equipment are subjected to high-temperature oxidation and corrosion. Research and development of efficient protective coatings is the main task in the field. Also, knowledge about the depletion state of the coating during the operation time is important. To date, practical nondestructive methods for the measurement of the depletion state do not exist. By integrating magnetic phases into the coating, the condition of the coating can be determined by measuring its magnetic properties. In this paper, a new technique using frequency mixing is proposed to investigate the thickness of the coatings based on their magnetic properties. A sensor system is designed and tested on specific magnetic coatings. New approaches are proposed to overcome the dependency of the measurement on the distance between coil and sample that all noncontact techniques face. The novelty is a low cost sensor with high sensibility and selectivity which can provide very high signal-to-noise ratios. Prospects and limitations are discussed for future use of the sensor in industrial applications.

Aseptic loosening of total joint replacements is caused by wear debris-induced osteoclastic bone resorption, for which bisphosphonates (BPs) and RANK antagonists have been developed. Although BPs are effective in preventing metabolic bone loss, they are less effective for inflammatory bone loss. Because this difference has been attributed to the antiapoptotic inflammatory signals that protect osteoclasts from BP-induced apoptosis, but not RANK antagonists, we tested the hypothesis that osteoprotegerin (OPG) is more effective in preventing wear debris-induced osteolysis than zoledronic acid (ZA) or alendronate (Aln) in the murine calvaria model using in vivo micro-CT and traditional histology. Although micro-CT proved to be incompatible with titanium (Ti) particles, we were able to demonstrate a 3.2-fold increase in osteolytic volume over 10 days induced by polyethylene (PE) particles versus sham controls (0.49 +/- 0.23 mm(3) versus 0.15 +/- 0.067 mm(3); p < 0.01). Although OPG and high-dose ZA completely inhibited this PE-induced osteolysis (p < 0.001), pharmacological doses of ZA and Aln were less effective but still reached statistical significance (p < 0.05). Traditional histomorphometry of the sagital suture area of calvaria from both Ti and PE-treated mice confirmed the remarkable suppression of resorption by OPG (p < 0.001) versus the lack of effect by physiological BPs. The differences in drug effects on osteolysis were largely explained by the significant difference in osteoclast numbers observed between OPG versus BPs in both Ti- and PE-treated calvaria; and linear regression analyses that demonstrated a highly significant correlation between osteolysis volume and sagittal suture area versus osteoclast numbers (p < 0.001)., ((c) 2008 Orthopaedic Research Society.)

Purpose: To investigate whether amifostine can reduce radiation hematotoxicity., Patients and Methods: Seventy-three patients undergoing radiotherapy for squamous cell carcinoma of the head and neck at the university clinics of Freiburg, Heidelberg, and Erlangen were evaluated. All received 60 Gy (50-70 Gy) at 5 x 2 Gy fractions per week employing standard techniques. Thirty-five were randomized to receive 200 mg/m(2) amifostine i.v. 30 min before radiation; 38 served as control patients. Blood counts (total n = 501) were determined before, during, and while completing radiotherapy. Changes of leukocyte, platelet, and hemoglobin levels were determined and compared using the t test., Results: The blood hemoglobin level and the platelet count were not affected by irradiation, for either the amifostine-treated or control patients. Similarly, the leukocyte counts of amifostine-treated patients did not change during irradiation. However, control patients experienced a decrease in leukocyte count from 8.1 x 10(3)/mm(3) to 5.8 x 10(3)/mm(3) (difference: 2.3 x 10(3)/mm(3)). This seems to be line specific: Whereas amifostine does not affect lymphocyte count, a radiation-induced decrease of neutrophil granulocytes seems to be prevented., Conclusion: Amifostine protects from radiation hematotoxicity, particularly affecting the granulocytopoiesis. These data confirm results from our former study.

Purpose: To evaluate the influence of blood hemoglobin concentration on the radiosensitivity of acutely reacting normal tissues., Methods and Materials: Weekly scores (EORTC/RTOG criteria) for acute reactions of skin and mucosa are available for 60 patients with cancer of the head and neck undergoing a standard conventional radiotherapy. The prognostic significance of blood hemoglobin levels on the development of acute reactions is studied by multivariate analysis (Cox Proportional Hazards Model). Further, the incidence and the time to development of these reactions is looked at in cohorts of patients with different mean blood hemoglobin concentrations during radiotherapy. Patients are therefore classified into a "severely anemic group" (hemoglobin < 11.0 g/100 mL), and into a cohort with a blood hemoglobin value equal or above 11.0 g/100 mL., Results: Normal tissue scoring and monitoring of blood hemoglobin levels allows for a detailed analysis of possible correlations. A decrease in the mean blood hemoglobin value of 1 g/100 mL predicts a reduced risk to develop a skin reaction of Grade 2 or 3 (RR = 0.9; p = 0.08; RR = 0.8; p = 0.26, respectively) or a mucosa reaction of Grade 3 (RR = 0.8; p = 0.16), independent from the radiation dose, the treatment time and from previous surgery within the radiation volume (multivariate analysis). Likewise, patients with severe anemia develop grade 3 mucositis or dermatitis less often (0%; 13%) as compared to those with blood hemoglobin concentrations equal or above 11.0 g/100 mL (21%; 19%). Skin and mucosa reactions further tend to occur later in the course of radiation. The observations are not statistically significant and possible reasons will be discussed., Conclusions: A decreased blood hemoglobin concentration may-perhaps by an impaired tissue oxygenation-reduce the radiosensitivity of normal tissue such as skin and mucosa. However, the data is preliminary and needs further confirmation.

Background: Radiotherapy--even of small volumes--can decrease leukocyte counts. We examined whether the radio-protector amifostine can reduce this hematotoxicity., Patients and Methods: Twenty-six patients (Table 1) undergoing radiotherapy for squamous cell carcinoma of the head and neck were evaluated. All were given 60 (to 70) Gy 5 x 2 Gy per week in standard radiation techniques. Thirteen patients are randomized to receive 200 mg/m2 amifostine i.v., 30 minutes before radiation. Blood counts and differentials were determined before, during and following radiotherapy. Differences of these parameters are calculated and compared by t-test., Results: The blood hemoglobin and the thrombocyte levels did not change during the radiotherapy course, neither for the amifostine treated, nor the control patients. Similarly the leukocyte counts of amifostine treated patients did not change during irradiation. The control patients, however, had a decrease of leukocytes from 8.4 to 6.0 x 10(3)/microliter, p = 0.03 (Table 2), and the reduction of the neutrophilic granulocyte count was more impressive for these patients., Conclusion: In this explorative study amifostine diminished radiation induced leukocyte toxicity.

Current treatments for human immunodeficiency virus (HIV) include both reverse transcriptase and protease inhibitors. Results from in vitro and clinical studies suggest that combination therapy can be more effective than single drugs in reducing viral burden. To evaluate compounds for combination therapy, stavudine (d4T), didanosine (ddI), or BMS-186,318, an HIV protease inhibitor, were combined with other clinically relevant compounds and tested in a T-cell line (CEM-SS) that was infected with HIV-RF or in peripheral blood mononuclear cells infected with a clinical HIV isolate. The combined drug effects were analyzed by the methods described by Chou and Talalay (Adv. Enzyme Regul. 22:27-55, 1984) as well as by Prichard et al. (Antimicrob. Agents Chemother. 37:540-545, 1993). The results showed that combining two nucleoside analogs (d4T-ddI, d4T-zidovudine [AZT], and d4T-zalcitabine [ddC]), two HIV protease inhibitors (BMS-186,318-saquinavir, BMS-186,318-SC-52151, and BMS-186,318-MK-639) or a reverse transcriptase and a protease inhibitor (BMS-186,318-d4T, BMS-186,318-ddI, BMS-186,318-AZT, d4T-saquinavir, d4T-MK-639, and ddI-MK-639) yielded additive to synergistic antiviral effects. In general, analysis of data by either method gave consistent results. In addition, combined antiviral treatments involving nucleoside analogs gave slightly different outcomes in the two cell types, presumably because of a difference in phosphorylation patterns. Importantly, no strong antagonism was observed with the drug combinations studied. These data should provide useful information for the design of clinical trials of combined chemotherapy.

The observed in vitro and in vivo benefit of combination treatment with anti-human immunodeficiency virus (HIV) agents prompted us to examine the potential of resistance development when two protease inhibitors are used concurrently. Recombinant HIV-1 (NL4-3) proteases containing combined resistance mutations associated with BMS-186318 and A-77003 (or saquinavir) were either inactive or had impaired enzyme activity. Subsequent construction of HIV-1 (NL4-3) proviral clones containing the same mutations yielded viruses that were severely impaired in growth or nonviable, confirming that combination therapy may be advantageous. However, passage of BMS-186318-resistant HIV-1 (RF) in the presence of either saquinavir or SC52151, which represented sequential drug treatment, produced viable viruses resistant to both BMS-186318 and the second compound. The predominant breakthrough virus contained the G48V/A71T/V82A protease mutations. The clone-purified RF (G48V/A71T/V82A) virus, unlike the corresponding defective NL4-3 triple mutant, grew well and displayed cross-resistance to four distinct protease inhibitors. Chimeric virus and in vitro mutagenesis studies indicated that the RF-specific protease sequence, specifically the Ile at residue 10, enabled the NL4-3 strain with the triple mutant to grow. Our results clearly indicate that viral genetic background will play a key role in determining whether cross-resistance variants will arise.

The human immunodeficiency virus (HIV) fusion inhibitor siamycin I, a 21-residue tricyclic peptide, was identified from a Streptomyces culture by using a cell fusion assay involving cocultivation of HeLa-CD4+ cells and monkey kidney (BSC-1) cells expressing the HIV envelope gp160. Siamycin I is effective against acute HIV type 1 (HIV-1) and HIV-2 infections, with 50% effective doses ranging from 0.05 to 5.7 microM, and the concentration resulting in a 50% decrease in cell viability in the absence of viral infection is 150 microM in CEM-SS cells. Siamycin I inhibits fusion between C8166 cells and CEM-SS cells chronically infected with HIV (50% effective dose of 0.08 microM) but has no effect on Sendai virus-induced fusion or murine myoblast fusion. Siamycin I does not inhibit gp120 binding to CD4 in either gp120- or CD4-based capture enzyme-linked immunosorbent assays. Inhibition of HIV-induced fusion by this compound is reversible, suggesting that siamycin I binds noncovalently. An HIV-1 resistant variant was selected by in vitro passage of virus in the presence of increasing concentrations of siamycin I. Drug susceptibility studies on a chimeric virus containing the envelope gene from the siamycin I-resistant variant indicate that resistance maps to the gp160 gene. Envelope-deficient HIV complemented with gp160 from siamycin I-resistant HIV also displayed a resistant phenotype upon infection of HeLa-CD4-LTR-beta-gal cells. A comparison of the DNA sequences of the envelope genes from the resistant and parent viruses revealed a total of six amino acid changes. Together these results indicate that siamycin I interacts with the HIV envelope protein.

Development of viral resistance to the aminodiol human immunodeficiency virus (HIV) protease inhibitor BMS 186,318 was studied by serial passage of HIV type 1 RF in MT-2 cells in the presence of increasing concentrations of compound. After 11 passages, an HIV variant that showed a 15-fold increase in 50% effective dose emerged. This HIV variant displays low-level cross-resistance to the C2 symmetric inhibitor A-77003 but remains sensitive to the protease inhibitors Ro 31-8959 and SC52151. Genetic analysis of the protease gene from a drug-resistant variant revealed an Ala-to-Thr change at amino acid residue 71 (A71T) and a Val-to-Ala change at residue 82 (V82A). To determine the effects of these mutations on protease and virus drug susceptibility, recombinant protease and proviral HIV type 1 clones containing the single mutations A71T and V82A or double mutation A71T/V82A were constructed. Subsequent drug sensitivity assays on the mutant proteases and viruses indicated that the V82A substitution was responsible for most of the resistance observed. Further genotypic analysis of the protease genes from earlier passages of virus indicated that the A71T mutation emerged prior to the V82A change. Finally, the level of resistance did not increase following continued passage in increasing concentrations of drug, and the resistant virus retained its drug susceptibility phenotype 34 days after drug withdrawal.

A series of aminodiol inhibitors of human immunodeficiency virus type 1 (HIV-1) protease were identified by using an in vitro peptide cleavage assay. BMS 182,193, BMS 186,318, and BMS 187,071 protected cells against HIV-1, HIV-2, and simian immunodeficiency virus infections, with 50% effective doses ranging from 0.05 to 0.33 microM, while having no inhibitory effect on cells infected with unrelated viruses. These compounds were also effective in inhibiting p24 production in peripheral blood mononuclear cells infected with HIV-1 IIIB and against the zidovudine-resistant HIV-1 strain A018C. Time-of-addition studies indicated that BMS 182,193 could be added as late as 27 h after infection and still retain its antiviral activity. To directly show that the activity of these compounds in culture was due to inhibition of proteolytic cleavage, the levels of HIV-1 gag processing in chronically infected cells were monitored by Western blot (immunoblot) analysis. All compounds blocked the processing of p55 in a dose-dependent manner, with 50% effective doses of 0.4 to 2.4 microM. To examine the reversibility of BMS 186,318, chronically infected CEM-SS cells were treated with drug and virions purified from the culture medium. Incubation of HIV-1 particles in drug-free medium indicated that inhibition of p55 proteolysis was slowly reversible. The potent inhibition of HIV-1 during both acute and chronic infections indicates that these aminodiol compounds are effective anti-HIV-1 compounds.

Development of stavudine resistance was studied using human immunodeficiency virus type 1 isolates from 13 patients treated with stavudine for 18-22 months. Drug sensitivity testing on 11 of these pre- and posttherapy isolates identified only 2 posttreatment isolates with decreased stavudine sensitivity (ED50s < 4-fold higher than the average pretreatment ED50). Genotypic analysis of all 13 pairs of isolates identified multiple mutations in the reverse transcriptase (RT) gene. However, no genetic basis was identified to account for the observed changes in stavudine susceptibility. A recombinant virus containing the entire RT gene of the posttherapy isolate displaying the greatest resistance remained sensitive to stavudine. Five of the stavudine posttreatment isolates developed resistance (9- to 176-fold) to zidovudine, although the relationship between stavudine treatment and the appearance of zidovudine resistance remains unexplained. Analysis of 10 additional pairs of isolates did not confirm this relationship. The low frequency and modest degree of change in stavudine sensitivity following prolonged treatment is very encouraging.

A novel substituted naphthalenone (TGG-II-23A) has been found that inhibits HIV-1 infection of CEM-SS cells at concentrations that are not cytotoxic. Time of addition experiments indicate that TGG-II-23A functions at a stage of the HIV-1 life cycle at or near reverse transcription. Cell free assays confirmed that TGG-II-23A inhibits HIV-1 reverse transcriptase. Similar to other non-nucleoside inhibitors, TGG-II-23A was specific for HIV-1 and failed to inhibit the replication of HIV-2. The binding site of TGG-II-23A appears to be in close proximity to that of the TIBO-like inhibitors, since a TIBO-resistant HIV-1 was also resistant to TGG-II-23A treatment. TGG-II-23A is a mixed non-competitive inhibitor that exhibits the same template:primer selectivity as other non-nucleoside inhibitors. TGG-II-23A therefore represents a new structural entry into the TIBO/Nevirapine class of inhibitors of HIV-1 reverse transcriptase.