Double-blind trial of dapsone against placebo in the treatment of rheumatoid arthritis

Research Supporting a Pilot Study of Metronomic Dapsone during Glioblastoma Chemoirradiation

This short note presents previous research data supporting a pilot study of metronomic dapsone during the entire course of glioblastoma treatment. The reviewed data indicate that neutrophils are an integral part of human glioblastoma pathophysiology, contributing to or facilitating glioblastoma growth and treatment resistance. Neutrophils collect within glioblastoma by chemotaxis along several chemokine/cytokine gradients, prominently among which is interleukin-8. Old data from dermatology research has shown that the old and inexpensive generic drug dapsone inhibits neutrophils' chemotaxis along interleukin-8 gradients. It is on that basis that dapsone is used to treat neutrophilic dermatoses, for example, dermatitis herpetiformis, bullous pemphigoid, erlotinib-related rash, and others. The hypothesis of this paper is that dapsone will reduce glioblastomas' neutrophil accumulations by the same mechanisms by which it reduces dermal neutrophil accumulations in the neutrophilic dermatoses. Dapsone would thereby reduce neutrophils' contributions to glioblastoma growth. Dapsone is not an ideal drug, however. It generates methemoglobinemia that occasionally is symptomatic. This generation is reduced by concomitant use of the antacid drug cimetidine. Given the uniform lethality of glioblastoma as of 2020, the risks of dapsone 100 mg twice daily and cimetidine 400 mg twice daily is low enough to warrant a judicious pilot study.

Metabolism of drugs by leukocytes

Neutrophils and monocytes can metabolize drugs to reactive metabolites, especially those drugs that have nitrogen or sulfur in a low oxidation state. The major system involved in this oxidation is the combination of NADPH oxidase and myeloperoxidase which generates HOCl. Although this system is unlikely to be quantitatively important, i.e. it is unlikely to have a significant effect on the pharmacokinetics of a drug, the reactive metabolites produced appear to have significant biological effects. Reactive metabolites, by their very nature, have short half-lives, and most of their effects will be exerted on the cells that formed them. Therefore, they are likely to be important for adverse reactions that involve leukocytes, such as agranulocytosis and immune-mediated reactions. However, the mechanism of these reactions is unknown and evidence for the association of leukocyte-derived reactive metabolites with such reactions is circumstantial at present. There is also circumstantial evidence to link the formation of such reactive metabolites to the antiinflammatory effects of some drugs. Possible mechanisms include the scavenging of other reactive species or inhibition of cells, especially neutrophils and macrophages, involved in inflammation. The oxidation of drugs by leukocytes requires activation of the cells; therefore, infection or other inflammatory conditions that activate leukocytes may represent one of the risk factors for idiosyncratic drug reactions.

Dapsone and sulfones in dermatology: overview and update

In their 60-year history, dapsone and the sulfones have been used as both antibacterial and anti-inflammatory agents. Dapsone has been used successfully to treat a range of dermatologic disorders, most successfully those characterized by abnormal neutrophil and eosinophil accumulation. This article reviews and updates the chemistry, pharmacokinetics, clinical application, mechanism of action, adverse effects, and drug interactions of dapsone and the sulfones in dermatology.

Discovery of FR115092: a novel antinephritic agent

A series of dapsone-related 4-aminopheynl and 2-aminothiazolyl derivatives was prepared, and their antinephritic activity and blood toxicity were evaluated. 5-(2-Pyridylsulfonyl)-2-thiazolamine (FR115092, 26) was effective against two nephritis models, namely graft-versus-host disease (GVHD) and autoimmune W/BF1 mice, and showed none of the blood toxicity observed with dapsone.

Dapsone in rheumatoid arthritis

Dapsone, a synthetic sulfone with chemical similarities to sulfapyridine, has been used for a number of years to treat leprosy and dermatitis herpetiformis. Recently, a number of prospective, randomized, double-blind trials have shown their success in the management of rheumatoid arthritis, with dapsone being superior to placebo and comparable to chloroquine and hydroxychloroquine. Its mode of anti-inflammatory actions in rheumatoid arthritis is not clearly understood, but modulation of neutrophil activity or inhibition of neutrophil inflammatory product formation or release appear to play a role. The major limiting side effect is hemolytic anemia, which may be mitigated through careful patient selection, conservative drug dosing, close monitoring, and possibly, concurrent administration of antioxidants or cytochrome P450 inhibitors. Methemoglobinemia is another common finding among patients receiving dapsone therapy, but rarely does it result in prominent symptoms other than transient pallor. Less common adverse events to dapsone include the idiosyncratic reactions of leukopenia and agranulocytosis, cutaneous eruptions, peripheral neuropathy, psychosis, toxic hepatitis, cholestatic jaundice, nephrotic syndrome, renal papillary necrosis, severe hypoalbuminemia without proteinuria, an infectious mononucleosis-like syndrome, and minor neurological and gastrointestinal complaints. In this report, two patients with advanced rheumatoid arthritis, who were safely and effectively treated with dapsone after failure with other second-line agents, are described and the literature is reviewed. We suggest that dapsone is an effective second-line agent in the treatment of rheumatoid arthritis.

Antimicrobial therapy for rheumatoid arthritis

New interest in the use of antibiotics in the treatment of arthritis was stimulated by two factors: (1) observations that, in some forms of chronic arthritis, microbial antigens persist in the synovial membrane, and (2) the increasing knowledge of the anti-inflammatory and immunosuppressive effects of antibiotics. Recently, several published controlled studies reported a beneficial effect of tetracyclines on RA and reactive arthritis. Whether the anti-arthritic activity of the tetracyclines investigated is mediated by the antimicrobial, anti-inflammatory or immunomodulatory properties remains to be determined. It may be concluded from these studies that tetracyclines have a beneficial effect on RA, especially when laboratory parameters are considered. The effect on the clinical parameters is not unequivocal. The adverse effects seem to be mild but the long-term efficacy and safety of tetracyclines as disease-modifying antirheumatic drugs remain to be demonstrated.

A double-blind comparative study of hydroxychloroquine and dapsone, alone and in combination, in rheumatoid arthritis

Eighty patients with active rheumatoid arthritis (RA) entered a double-blind randomized study of 24 weeks duration, to compare the efficacy and toxicity of hydroxychloroquine, dapsone, and a combination of both drugs in treatment of RA. Evaluation of changes in clinical, laboratory and radiologic variables was based on 63 patients completing the trial. There was no clear difference between the three therapy groups in most inflammatory variables after 24 weeks. However, only patients receiving the combination therapy improved significantly in all clinical and laboratory variables. Nine patients in the combination group and four in each single drug group discontinued during the trial, mainly because of toxicity. Four patients taking the combination therapy withdrew because of hemolytic anemia, and none in the dapsone group. These findings suggest that hydroxychloroquine in combination with dapsone is somewhat more effective and less tolerated than single drug treatments.

Scleritis in relapsing polychondritis. Response to therapy

The authors reviewed the records of 11 patients with relapsing polychondritis associated with active scleritis and analyzed the immunopathologic characteristics of ocular tissue from three of these. Seven patients (63%) required cytotoxic drugs, alone or in combination with low-dose oral corticosteroids. Only one patient was treated successfully with systemic corticosteroids alone. Two patients were controlled with dapsone and one with an oral nonsteroidal anti-inflammatory drug. Dapsone, which has been reported to be effective in the treatment of relapsing polychondritis, did not control the destructive scleral inflammation in six (75%) of eight patients; two (50%) of four patients with diffuse anterior scleritis were controlled with this drug. Patients with nodular and necrotizing scleritis were controlled with azathioprine and cyclophosphamide, respectively. These data suggest that the ocular manifestations of relapsing polychondritis, especially nodular and necrotizing scleritis, are less amenable to treatment with systemic corticosteroids and/or dapsone and that more potent immunosuppressants (azathioprine and cyclophosphamide) may be required to treat these lesions successfully. Results of histologic and immunofluorescent examination of conjunctival and/or scleral biopsy specimens from three patients confirmed the vasculitic nature of the eye lesions in this disease.

Drug metabolism by leukocytes and its role in drug-induced lupus and other idiosyncratic drug reactions

This review presents a unifying hypothesis that provides a connection between several types of hypersensitivity reactions associated with several types of drugs and explains some of the therapeutic effects (antiinflammatory activity and antithyroid effects) of these same drugs. This hypothesis centers on the oxidation of these drugs to chemically reactive metabolites by peroxidases. The drugs of interest have functional groups that are easily oxidized. The major peroxidase involved in this hypothesis is MPO because of its critical location in leukocytes which play a key role in the function of the immune system. However, thyroid peroxidase can probably also oxidize many of the same drugs to reactive metabolites, and this may be responsible for the thyroid autoimmunity observed in connection with some hypersensitivity reactions. Peroxidases have also been described in the skin and in platelets, and their presence may be responsible for the high incidence of skin reactions in the hypersensitivity response and the occurrence of immune-mediated thrombocytopenia, respectively. Involvement of other peroxidases, such as prostaglandin peroxidase, may also be important for antiinflammatory effects of drugs. In addition, leukocytes contain prostaglandin synthetase, and the activation of leukocytes leads to the release of arachidonic acid and the production of prostaglandins. This process may also lead to the metabolism of drugs to reactive metabolites. In studies of the metabolism of procainamide and dapsone, aspirin and indomethacin did not inhibit the formation of the hydroxylamine by neutrophils and mononuclear leukocytes. This is evidence against the involvement of prostaglandin synthetase in these oxidation; however, preliminary studies with other drugs suggest that prostaglandin synthetase may contribute to the metabolism of some drugs by leukocytes. Furthermore, the metabolism of phenylbutazone, phenytoin, and tenoxicam, as well as our preliminary work with other drugs such as carbamazepine, suggests that the range of drugs that are metabolized to reactive metabolites by peroxidases may be broader than initially suspected. There are several other drugs that do not fit into the functional group classes covered in this review but have similar properties. A good example is alpha-methyldopa, which is associated with drug-induced lupus, immune-mediated hemolytic anemia, and other hypersensitivity reactions. Such drugs may also be metabolized to reactive metabolites by peroxidases. Another aspect of the hypothesis is that an infection, or other inflammatory condition, may be an important risk factor for a hypersensitivity reaction because such a stimulus leads to activation of leukocytes which can lead to formation of reactive metabolites from certain drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioactivation of dapsone to a cytotoxic metabolite by human hepatic microsomal enzymes

1. Using human mononuclear leucocytes as target cells, we have investigated the bioactivation of dapsone (DDS) to a cytotoxic metabolite in the presence of microsomes from nine human livers. Values for NADPH dependent toxicity ranged from 8.8-27% (15.8 +/- 5.9%) and were similar to those for microsomes from control mice, 16-24% (19.0 +/- 4.8%). 2. Microsomes prepared from mice induced with either phenobarbitone or beta-naphthoflavone did not produce significantly more NADPH dependent toxicity than microsomes prepared from control mice. 3. Cytotoxicity was abolished not only by ascorbic acid, but also by sub-physiological concentrations of N-acetylcysteine and glutathione. 4. DDS was metabolised in vitro to a hydroxylamine (metabolic conversion 3.1 +/- 1.5%), which was oxidised further to a cytotoxic metabolite which also became irreversibly bound to protein.

Adjuvant therapy of bullous pemphigoid with dapsone

Thirteen patients with recurrent severe widespread recalcitrant bullous pemphigoid (BP) were studied. These patients had been initially treated with prednisone and azathioprine, and clinically responded. However, they frequently continued to have flare-ups or activation of the disease while still on treatment with high doses of these drugs. The addition of dapsone, as an adjuvant to the treatment, helped to produce a complete clinical remission in 12 patients (92%). In addition, there was a statistically significant difference in the median dose of prednisone, before and after the institution of dapsone, and in the maintenance dose of prednisone. Patients were tapered off prednisone more easily than before and did not flare at lower doses of prednisone as previously. It is suggested that, in patients with severe, recalcitrant, recurrent disease, the addition of dapsone to the existing regime of corticosteroids and/or immunosuppressive drugs, may be beneficial. This may be especially valuable to patients in whom corticosteroids have been used for prolonged periods and in whom increasing the corticosteroid dose further may be associated with significant side-effects.

Outcome of attempts to treat rheumatoid arthritis with gold, penicillamine, sulphasalazine, or dapsone

The outcome of attempts to continue treatment indefinitely with either gold, penicillamine, sulphasalazine, or dapsone was studied in 240 patients with rheumatoid arthritis (RA). The usual reason for discontinuing treatment was the occurrence of an adverse effect. This led to 53% of patients stopping gold, 33% sulphasalazine, 32% penicillamine, and 17% dapsone. The next most frequent reason was that the drug was ineffective, leading to discontinuation in 37% of patients having dapsone, 24% sulphasalazine, 19% penicillamine, and 16% gold. Other reasons for stopping treatment were infrequent. The high discontinuation rate of these drugs over 2 years in part accounts for the conflict of opinion on whether they can alter the course of RA; their efficacy must to a large extent be governed by their acceptability.

Report on chloroquine and dapsone in the treatment of rheumatoid arthritis: a 6-month comparative study

A controlled study compared 6 months' treatment of 60 patients with rheumatoid arthritis (RA). Half were randomly allocated to treatment with chloroquine 250 mg daily, the other half dapsone 100 mg daily (50 mg/day for the first 7 days) following a one-month run-in assessment period. All patients had active or progressing disease. Both treatment groups showed significant improvement in morning stiffness, number of painful joints, pain scores, Ritchie index, and proximal interphalangeal joint size, and the chloroquine group alone in grip strength. Laboratory tests showed significant decreases in erythrocyte sedimentation rate, C-reactive protein, and total serum protein levels, with significant increase in serum albumin in the dapsone group, where there was a significant mean drop in haemoglobin (less than 1 g/dl) and a rise in serum bilirubin, associated with its haemolytic effect. X-ray erosion scores were not significantly affected. The clinical and laboratory responses became evident by the time of the 2-month assessment. Criteria for clinical and laboratory improvement were defined, according to which there were 21/26 improvers in the chloroquine group and 12/29 in the dapsone group. It is concluded that although both are effective preparations, chloroquine showed a significantly higher improvement rate and was certainly better tolerated. It is the preferred treatment for patients with active or progressive disease not controlled by nonsteroidal anti-inflammatory drugs, with dapsone as an alternative for patients who fail to respond to or cannot tolerate chloroquine.

Comparison between penicillamine and sulphasalazine in rheumatoid arthritis: Leeds-Birmingham trial

Sulphasalazine was first formulated by Svartz in the early 1940s, specifically for use as a remission inducing drug in rheumatoid arthritis. After the publication of an unfavourable trial, however, the drug was restricted to patients with ulcerative colitis. In the late 1970s sulphasalazine was re-examined in rheumatoid arthritis and favourable results reported in "open" trials. A double blind controlled trial was therefore conducted comparing enteric coated sulphasalazine and D-penicillamine in patients with active rheumatoid arthritis. A total of 63 patients were recruited in two centres; 31 were treated with sulphasalazine and 32 received penicillamine. After 16 weeks' treatment both drugs had produced significant improvements in clinical score, pain score measured on a visual analogue scale, grip strength, Ritchie articular index, erythrocyte sedimentation rate, and serum C reactive protein concentration. Nausea was the major side effect in the sulphasalazine treated group. No potentially dangerous effects of sulphasalazine were encountered in contrast with those seen in the penicillamine group. The results suggest that sulphasalazine is an effective and safe drug capable of producing remissions in active rheumatoid arthritis. They also lend confidence to the use of preliminary "open" trials as a means of screening for remission inducing drugs in rheumatoid arthritis.