Mark L. Nelson

British HIV Association guidelines for the treatment of HIV-1-positive adults with antiretroviral therapy 2015

Writing Group Duncan Churchill, Chair, Royal Sussex County Hospital, Brighton, UK Laura Waters, Vice Chair, Mortimer Market Centre, London, UK Nadia Ahmed, Mortimer Market Centre, London, UK Brian Angus, University of Oxford, UK Marta Boffito, Chelsea and Westminster Hospital, London, UK Mark Bower, Chelsea and Westminster Hospital, London, UK David Dunn, University College London, UK Simon Edwards, Central and North West London NHS Foundation Trust, UK Carol Emerson, Royal Victoria Hospital, Belfast, UK Sarah Fidler, Imperial College School of Medicine at St Mary’s, London, UK †Martin Fisher, Royal Sussex County Hospital, Brighton, UK Rob Horne, University College London, UK Saye Khoo, University of Liverpool, UK Clifford Leen, Western General Hospital, Edinburgh, UK Nicola Mackie, Imperial College Healthcare NHS Trust, London, UK Neal Marshall, Royal Free Hospital NHS Trust, London, UK Fernando Monteiro, UK-CAB Mark Nelson, Chelsea and Westminster Hospital NHS Foundation Trust, London, UK

The history of the tetracyclines

The history of the tetracyclines involves the collective contributions of thousands of dedicated researchers, scientists, clinicians, and business executives over the course of more than 60 years. Discovered as natural products from actinomycetes soil bacteria, the tetracyclines were first reported in the scientific literature in 1948. They were noted for their broad spectrum antibacterial activity and were commercialized with clinical success beginning in the late 1940s to the early 1950s. The second‐generation semisynthetic analogs and more recent third‐generation compounds show the continued evolution of the tetracycline scaffold toward derivatives with increased potency as well as efficacy against tetracycline‐resistant bacteria, with improved pharmacokinetic and chemical properties. Their biologic activity against a wide spectrum of microbial pathogens and their uses in mammalian models of inflammation, neurodegeneration, and other biological systems indicate that the tetracyclines will continue to be successful therapeutics in infectious diseases and as potential therapeutics against inflammation‐based mammalian cell diseases.

Tetracyclines That Promote SMN2 Exon 7 Splicing as Therapeutics for Spinal Muscular Atrophy

Tetracycline derivatives increase exon 7 splicing during RNA processing of the spinal muscular atrophy–modifying gene SMN2, which may prove therapeutically useful. Correcting Splicing to Prevent Spinal Muscular Atrophy Even before birth, a child with the most severe form of spinal muscular atrophy (SMA) may be frail, so that the mother feels only faint fetal movements during the last months of pregnancy. After birth, children with this autosomal recessive disease exhibit weak muscles, swallowing difficulties, and respiratory problems, often dying within the first 2 years of life. These symptoms are caused by the degeneration of certain motor neurons in the spinal cord, resulting in muscle weakness and shrinking. There is no cure or effective therapy for SMA, which kills more infants than any other genetic disorder. Now, Krainer and colleagues describe a compound with promise as an SMA therapeutic. SMA is usually caused by loss-of-function mutations in the SMN1 gene, which encodes a protein that aids in the assembly of the spliceosome. This large protein-RNA complex removes introns from RNA transcripts to create mature mRNAs. An inadequate amount of SMN protein causes SMA, but it is not clear why the deficiency selectively affects spinal cord motor neurons. Cells contain a second source of the SMN protein, the SMN2 gene. Because of a single nucleotide change in SMN2, its RNA transcript is usually spliced incorrectly, such that exon 7 is left out; the encoded truncated protein is quite unstable. Thus, one way to treat SMA would be to correct SMN2 splicing. Although compounds have been identified that increase the production of full-length SMN protein from SMN2, they act in a relatively nonspecific manner; some are toxic. A better possibility might be a drug that specifically alters splicing, potentially reducing side effects. The Hastings and Krainer labs, in collaboration with Paratek Pharmaceuticals, sought to identify a small molecule that specifically improves exon 7 splicing of SMN2 RNA in a cell-free assay. In a screen, they found one compound, a tetracycline derivative called PTK-SMA1, that could do this. PTK-SMA1 appears to stimulate exon 7 splicing in SMN1/2 specifically, not affecting splicing of other tested substrates. The researchers determined that PTK-SMA1 increases SMN protein concentrations both in fibroblasts derived from an SMA patient and in mouse models of SMA. Because PTK-SMA1 does not cross the blood-brain barrier but would need to do so in order to be therapeutically useful, the researchers now aim to modify PTK-SMA1 to achieve that end. Furthermore, as RNA splicing defects may contribute to other diseases, additional tetracycline derivatives that can repair specific splicing defects could potentially be identified and prove useful. There is at present no cure or effective therapy for spinal muscular atrophy (SMA), a neurodegenerative disease that is the leading genetic cause of infant mortality. SMA usually results from loss of the SMN1 (survival of motor neuron 1) gene, which leads to selective motor neuron degeneration. SMN2 is nearly identical to SMN1 but has a nucleotide replacement that causes exon 7 skipping, resulting in a truncated, unstable version of the SMA protein. SMN2 is present in all SMA patients, and correcting SMN2 splicing is a promising approach for SMA therapy. We identified a tetracycline-like compound, PTK-SMA1, which stimulates exon 7 splicing and increases SMN protein levels in vitro and in vivo in mice. Unlike previously identified molecules that stimulate SMN production via SMN2 promoter activation or undefined mechanisms, PTK-SMA1 is a unique therapeutic candidate in that it acts by directly stimulating splicing of exon 7. Synthetic small-molecule compounds such as PTK-SMA1 offer an alternative to antisense oligonucleotide therapies that are being developed as therapeutics for a number of disease-associated splicing defects.

Structure-Activity Relationship of the Aminomethylcyclines and the Discovery of Omadacycline

ABSTRACT A series of novel tetracycline derivatives were synthesized with the goal of creating new antibiotics that would be unaffected by the known tetracycline resistance mechanisms. New C-9-position derivatives of minocycline (the aminomethylcyclines [AMCs]) were tested for in vitro activity against Gram-positive strains containing known tetracycline resistance mechanisms of ribosomal protection (Tet M in Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae) and efflux (Tet K in S. aureus and Tet L in E. faecalis). A number of aminomethylcyclines with potent in vitro activity (MIC range of ≤0.06 to 2.0 μg/ml) were identified. These novel tetracyclines were more active against one or more of the resistant strains than the reference antibiotics tested (MIC range, 16 to 64 μg/ml). The AMC derivatives were active against bacteria resistant to tetracycline by both efflux and ribosomal protection mechanisms. This study identified the AMCs as a novel class of antibiotics evolved from tetracycline that exhibit potent activity in vitro against tetracycline-resistant Gram-positive bacteria, including pathogenic strains of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE). One derivative, 9-neopentylaminomethylminocycline (generic name omadacycline), was identified and is currently in human trials for acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP).

Ledipasvir–sofosbuvir for 6 weeks to treat acute hepatitis C virus genotype 1 or 4 infection in patients with HIV coinfection: an open-label, single-arm trial

BACKGROUND The latest European Association for the Study of the Liver (EASL) guidelines now recommend that patients with acute hepatitis C virus (HCV) infection should be treated with a combination of sofosbuvir and an NS5A inhibitor for 8 weeks. However, the ideal duration of treatment with interferon-free regimens, particularly in HIV-coinfected individuals, remains unknown. We assessed the efficacy and safety of 6 weeks of ledipasvir-sofosbuvir for acute genotype 1 or 4 HCV in HIV-1-coinfected patients. METHODS This open-label, single-arm trial, done in Germany and the UK, included patients with acute HCV genotype 1 or 4 and HIV-1. At screening, patients were either receiving HIV antiretrovirals and had HIV RNA less than 200 copies per mL, or not receiving antiretrovirals and had a CD4 T-cell count of greater than 500 cells per μL. All patients received ledipasvir-sofosbuvir once daily for 6 weeks. The primary efficacy endpoint was the proportion of patients with sustained virological response 12 weeks after the end of treatment (SVR12). This study is registered with ClinicalTrials.gov, number NCT02457611. FINDINGS Between June 11, 2015, and Jan 8, 2016, we enrolled and treated 26 patients. All (100%) were men, 24 (92%) were white, and 25 (96%) were receiving antiretroviral treatment. 19 (73%) had genotype 1a and seven (27%) had genotype 4 HCV. Overall, 20 (77%; 95% CI 56-91) of 26 patients achieved SVR12: 15 (79%) of 19 with genotype 1a, and five (71%) of seven with genotype 4. Of six patients not achieving SVR12, three relapsed, two achieved sustained virological response 4 weeks after the end of treatment but were lost to follow-up, and one was reinfected. The most common adverse events were fatigue (seven participants [27%]), nasopharyngitis (seven [27%]), and headache (six [23%]). No patient discontinued or interrupted therapy due to adverse events. No HIV rebound occurred during the study. INTERPRETATION The rate of cure with a fixed-dose combination of ledipasvir-sofosbuvir for patients with acute genotype 1 or 4 HCV infection and HIV-1 coinfection is similar to historic rates with interferon-based treatment, but with shorter treatment duration and more favourable safety outcomes. FUNDING Gilead Sciences.

Pharmacokinetics and Safety of Saquinavir/Ritonavir and Omeprazole in HIV-infected Subjects

We investigated the pharmacokinetics and safety of saquinavir/ritonavir when administered with omeprazole simultaneously and 2 h apart to human immunodeficiency virus (HIV) subjects. Saquinavir/ritonavir 12‐h pharmacokinetics was assessed with and without omeprazole 40 mg. Subjects were randomized to group A (saquinavir/ritonavir and omeprazole simultaneously/2 h apart) or group B (saquinavir/ritonavir and omeprazole 2 h apart/simultaneously). Saquinavir/ritonavir pharmacokinetics was assessed on days 1, 8, and 22. Within‐subject changes were evaluated by geometric mean ratios and 90% confidence interval (CI). Twelve subjects completed the study. GM (90% CI) for saquinavir area under the curve (AUC)0−12 (ng h/ml), trough concentration (Ctrough) (ng/ml), and maximum concentration (Cmax) (ng/ml) were 14,698 (13,242–20,636), 433 (368–758), 2,513 (2,243–3,329) without omeprazole; 22,646 (18,536–131,861), 750 (619–1,280), 3,890 (3,223–5,133) with omeprazole simultaneously; and 24,549 (20,884–38,894), 851 (720–1,782), 4,141 (3,554–5,992) with omeprazole 2 h earlier. Simultaneous administration of omeprazole significantly increased saquinavir AUC0−12, Ctrough, and Cmax by 54, 73, and 55%, whereas staggered administration by 67, 97, and 65%. No grade 3/4 toxicity or lab abnormalities were observed. In the presence of omeprazole, saquinavir plasma exposure is significantly increased in HIV‐infected subjects whether administered simultaneously or 2 h apart.

CSF/plasma HIV-1 RNA discordance even at low levels is associated with up-regulation of host inflammatory mediators in CSF

Highlights • Discordant HIV in CSF is associated with raised inflammatory mediators in CSF.• CSF mediators are raised with discordance both at high and low levels.• Discordance on ultrasensitive testing can also be also associated with raised mediators.

A global survey of HIV-positive people's attitudes towards cure research.

Involvement of people living with HIV (PLHIV) in the design of HIV cure studies is important, given the potential risks to participants. We present results of an international survey of PLHIV to define these issues and inform cure research.

In Vitro and In Vivo Antimalarial Efficacies of Optimized Tetracyclines

ABSTRACT With increasing resistance to existing antimalarials, there is an urgent need to discover new drugs at affordable prices for countries in which malaria is endemic. One approach to the development of new antimalarial drugs is to improve upon existing antimalarial agents, such as the tetracyclines. Tetracyclines exhibit potent, albeit relatively slow, action against malaria parasites, and doxycycline is used for both treatment (with other agents) and prevention of malaria. We synthesized 18 novel 7-position modified tetracycline derivatives and screened them for activity against cultured malaria parasites. Compounds with potent in vitro activity and other favorable drug properties were further tested in a rodent malaria model. Ten compounds inhibited the development of cultured Plasmodium falciparum with a 50% inhibitory concentration (IC50) after 96 h of incubation of <30 nM, demonstrating activity markedly superior to that of doxycycline (IC50 at 96 h of 320 nM). Most compounds showed little mammalian cell cytotoxicity and no evidence of in vitro phototoxicity. In a murine Plasmodium berghei model, 13 compounds demonstrated improved activity relative to that of doxycycline. In summary, 7-position modified tetracyclines offer improved activity against malaria parasites compared to doxycycline. Optimized compounds may allow lower doses for treatment and chemoprophylaxis. If safety margins are adequate, dosing in children, the group at greatest risk for malaria in countries in which it is endemic, may be feasible.

Reversing Tetracycline Resistance

The frequency of antibiotic resistance among common human and animal pathogens has continued to rise despite concerted efforts to improve antibiotic use and increase awareness of antibiotic resistance among providers and consumers of these valuable agents (1). Among hospital and community acquired infections, there are more than a dozen organisms whose multidrug resistance means that some individuals may contract infections for which there is only one drug with which to treat, or even in some instances, no drugs at all (Table 1). Among the latter organisms are the hospital acquired vancomycin-resistant Enterocoecus, Pseudomonas aeruginosa and Acinetobacter baumanii. The methicillin-resistant Staphylococcus aureus strains which have recently emerged with chromosomally-specified decreased susceptibility to vancomycin are also potentially the ones that could eventually be untreatable. In the community, Mycobacterium tuberculosis is a major problem with the Pneumococcus not far behind, especially as cephalosporin resistance rises and the use of this life-saving drug is lost. Vancomycin is the only drug left, used with a cephalosporin, to treat meningitis caused by the very common invasive pneumococcus.