Molecular mechanisms of resistance and treatment efficacy of clofazimine and bedaquiline against Mycobacterium tuberculosis

Clofazimine (CFZ) and bedaquiline (BDQ) are currently used for the treatment of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) strains. In recent years, adding CFZ and BDQ to tuberculosis (TB) drug regimens against MDR Mtb strains has significantly improved treatment results, but these improvements are threatened by the emergence of MDR and extensively drug-resistant (XDR) Mtb strains. Recently, CFZ and BDQ have attracted much attention for their strong clinical efficacy, although very little is known about the mechanisms of action, drug susceptibility test (DST), resistance mechanisms, cross-resistance, and pharmacokinetics of these two drugs. In this current review, we provide recent updates on the mechanisms of action, DST, associated mutations with individual resistance and cross-resistance, clinical efficacy, and pharmacokinetics of CFZ and BDQ against Mtb strains. Presently, known mechanisms of resistance for CFZ and/or BDQ include mutations within the Rv0678, pepQ, Rv1979c, and atpE genes. The cross-resistance between CFZ and BDQ may reduce available MDR-/XDR-TB treatment options. The use of CFZ and BDQ for treatment in the setting of limited DST could allow further spread of drug resistance. The DST and resistance knowledge are urgently needed where CFZ and BDQ resistance do emerge. Therefore, an in-depth understanding of clinical efficacy, DST, cross-resistance, and pharmacokinetics for CFZ and BDQ against Mtb can provide new ideas for improving treatment outcomes, reducing mortality, preventing drug resistance, and TB transmission. Along with this, it will also help to develop rapid molecular diagnostic tools as well as novel therapeutic drugs for TB.

Transdermal hormone replacement therapy improves vertebral bone density in primary biliary cirrhosis: results of a 1-year controlled trial

BACKGROUND

Retrospective studies have suggested that hormone replacement therapy may reduce the rate of bone loss in primary biliary cirrhosis, but no controlled data are available.

METHODS

Forty-two post-menopausal women with primary biliary cirrhosis were treated with calcium and vitamin D, either alone (n = 21) or together with transdermal hormone replacement therapy (n = 21). Bone densitometry was performed at baseline and at 1 year, and serum and urinary markers of bone turnover were measured at three-monthly intervals.

RESULTS

At entry, 17 patients (40%) had spinal or femoral osteopenia (T score - 1 to - 2.5) and nine (21%) had osteoporosis (T < - 2.5). In those given hormone replacement therapy, there was a significant decrease in the mean urinary deoxypyridinoline :creatinine ratios at 3 months (7.8 vs. 6.1 nm/mm creatinine for no hormone replacement therapy vs. hormone replacement therapy; P = 0.04) and a 48% reduction in urinary calcium excretion at 1 year (0.66 vs. 0.32 mm/mm creatinine; P = 0.01). Repeat bone densitometry at 1 year revealed a 2.25% increase in the hormone replacement therapy group (P = 0.02), compared with a non-significant 0.87% decrease in L2-L4 bone mineral density in those not given hormone replacement therapy. Both treatment regimens were well tolerated, with no increase in cholestasis.

CONCLUSIONS

Compared with calcium and vitamin D alone, supplemental treatment with transdermal hormone replacement therapy for 1 year improved the vertebral bone density and urinary markers of bone turnover in post-menopausal women with primary biliary cirrhosis.

Does active treatment of rheumatoid arthritis limit disease-associated bone loss?

OBJECTIVE

Generalized bone loss in rheumatoid arthritis (RA) is multi-factorial, with the inflammatory disease itself thought to contribute to bone loss. To study the extent to which control of disease activity affects bone turnover in RA and whether treatment with disease-modifying anti-rheumatic drugs (DMARDs) reduces bone turnover and loss of bone mass, we measured bone density and biochemical markers of bone resorption in a group of patients with active RA starting on DMARDS.

METHODS

Patients with active RA were enrolled on starting a new DMARD. Patients were mobile and none took steroids or any treatment for osteoporosis. Clinical and laboratory measures of disease activity were made at 3-monthly intervals and an index of disease activity (DAS) calculated. Bone density was assessed at 0, 1 and 2 yr (Hologic QDR 4500c). Urinary deoxypyridinoline (D-PYR) and pyridinoline (PYR) were measured by ELISA at 0, 3, 6, 9 and 12 months.

RESULTS

Forty patients were enrolled, mean age 59.5 (range 31-76), 26 female, 14 male, 25 had established RA, 15 had RA for <2 yr. Baseline D-PYR was elevated (8.4+/-4.55 nmol/mmol creatinine) and correlated with ESR (r=0.6, P<0.01) and DAS (r=0.4, P<0.05). On treatment ESR and DAS fell by 38.5 and 29.3%, respectively. D-PYR was reduced by 12.3% by 9 months (P<0.01). Spearman rank order correlation showed ESR to be the most significant determinant of D-PYR over 1 yr (r=0.43, P<0.001). Serial bone density was available on 21 patients. There was no significant change in BMD over the 2 yr. The change in DAS over 0-3 months showed an inverse relationship with the percent change in spine over 1 yr (r=-0.5, P=0.05). The change in D-PYR over 0-3 months was not closely related to the change in BMD at hip or spine at 1 yr.

CONCLUSION

Disease activity is a significant determinant of bone turnover in RA. Bone resorption markers fall on treatment of RA with DMARDs and no change in BMD was demonstrated at 2 yr. This study suggests the need to control disease activity in RA in order to prevent systemic bone loss.

Serum S100 concentrations are not useful in predicting micrometastatic disease in cutaneous malignant melanoma

BACKGROUND

S100 protein is an acidic calcium binding protein that is expressed by melanoma cells. Elevated serum values of S100 have been described in metastatic disease and it has been suggested that it may be used as an adjunct to staging and monitoring of treatment. Micrometastatic disease in the sentinel lymph node can be demonstrated by sentinel node biopsy (SNB) and the sentinel node status is known to be the most important predictor of relapse.

OBJECTIVES

To determine whether serum S100 concentrations could predict the presence of micrometastatic disease.

METHODS

Thirty-one patients with primary cutaneous melanoma > 1 mm were recruited from referrals to the Melanoma clinic. All patients had serum S100 concentrations evaluated prior to undergoing SNB. Serum S100 concentrations were established using an immunoluminometric method. Sentinel nodes were identified using a dual technique with both radiolabelled colloid (residual from preoperative lymphoscintigraphy) and blue dye according to the MD Anderson Cancer Center protocol. Results Nine of these 31 patients had evidence of micrometastatic disease on SNB. The mean serum S100 concentration of those with positive SNBs was 0.027 microg L-1 compared with 0.045 microg x L(-1) in patients with negative SNBs (normal < 0.14 microg x L(-1)). No patient in the study demonstrated raised concentrations of serum S100.

CONCLUSIONS

We conclude that serum S100 concentrations do not predict the presence of micrometastatic melanoma in sentinel nodes in primary cutaneous melanoma.

Measurement of markers of osteoclast and osteoblast activity in patients with acute and chronic diabetic Charcot neuroarthropathy

Excess osteoclast activity is believed to be responsible for the early bone changes associated with Charcot neuroarthropathy in diabetes mellitus. Markers of osteoclast and osteoblast activity were measured in four groups of patients: 16 with an acute Charcot foot, 16 with a chronic Charcot foot, 10 diabetic controls, and 10 non-diabetic controls. Serum carboxyterminal telopeptide of type 1 collagen (1CTP), a marker of osteoclastic bone resorption, was significantly raised in the dorsal venous arch of the acute Charcot foot, 6.1 +/- 1.5 microg l(-1) (mean +/- SD) compared with the chronic Charcot foot 4.1 +/- 1.4, diabetic controls 3.3 +/- 1.4, and non-diabetic controls 2.8 +/- 1.4, p < 0.0001. This local increase in 1CTP was also reflected systemically in a study subgroup of 6 patients with acute Charcot neuroarthropathy, in whom peripheral antecubital vein 1CTP was 9.2 +/- 2.6 compared with 9.0 +/- 3.1 in the foot. In 6 chronic Charcot neuroarthropathy patients, foot (3.8 +/- 1.3) and systemic (4.0 +/- 1.5) 1CTP values were similar. Serum procollagen carboxyterminal propeptide (P1CP), an indicator of osteoblastic bone formation, was not significantly different between the feet of patients with acute Charcot neuroarthropathy 112 +/- 1.5 microg l(-1), patients with chronic Charcot neuroarthropathy 109 +/- 1.5 microg l(-1), diabetic controls 93.5 +/- 2.3 microg l(-1), and non-diabetic controls 90.1 +/- 1.5 microg l(-1). These results suggest that the acute Charcot foot demonstrates excess osteoclastic activity without concomitant increase in osteoblastic function. This may be important in its pathogenesis.