The FDA has approved macitentan (ma" si ten' tan; Opsumit – Actelion), for oral treatment of pulmonary arterial hypertension (PAH). Macitentan is the second nonselective endothelin receptor antagonist approved for PAH. It is a derivative of bosentan (Tracleer), which is also manufactured by Actelion, and is scheduled to become available generically in 2015. Riociguat (Adempas), another new drug for this indication, will be reviewed in a future issue. Volibris

The FDA has approved obiltoxaximab (Anthim – Elusys Therapeutics), a toxin-targeting monoclonal antibody, for treatment of inhalational anthrax in combination with antibacterial drugs and prophylaxis of inhalational anthrax when other therapies are unavailable or inappropriate. Raxibacumab, another monoclonal antibody, was approved earlier for the same indication. Like raxibacumab, obiltoxaximab is being manufactured only for the CDC national stockpile and is not available for commercial sale.

The investigational monoclonal antibodies casirivimab and imdevimab (REGEN-COV – Regeneron) have been available in the US under an Emergency Use Authorization (EUA) since late 2020 for use together to treat mild to moderate COVID-19 in persons ≥12 years old who weigh ≥40 kg and are at high risk of progression to severe disease or hospitalization. The FDA has now expanded this EUA to allow use of the antibodies together for post-exposure prophylaxis of COVID-19 in such persons, if they are not fully vaccinated against COVID-19 or are unlikely to have an adequate immune response...

Tarlatamab-dlle (Imdelltra – Amgen), a first-in-class bispecific delta-like ligand 3 (DLL3)-directed CD3 T-cell engager, has received accelerated approval from the FDA for treatment of extensive-stage small cell lung cancer (SCLC) in adults who had disease progression on or after platinum-based chemotherapy. It is the first bispecific DLL3-directed CD3 T-cell engager to be approved in the US for this indication. Most patients with SCLC have a response to initial treatment, but progression generally occurs within a few months and overall survival is usually less than 8 months....

Marstacimab-hncq (Hympavzi – Pfizer), a tissue factor pathway inhibitor (TFPI) antagonist, has been approved by the FDA for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients ≥12 years old who have hemophilia A without factor VIII inhibitors or hemophilia B without factor IX inhibitors. It is the first hemophilia treatment to be approved in the US that targets an inhibitor of coagulation and the first to become available in prefilled pens and syringes for subcutaneous administration.

Penpulimab-kcqx (Anniko – Akeso Biopharma), a programmed death receptor-1 (PD-1)-blocking antibody, has been approved by the FDA for use in combination with cisplatin or carboplatin plus gemcitabine for first-line treatment of recurrent or metastatic nonkeratinizing nasopharyngeal carcinoma and for use as monotherapy for metastatic disease in adults with disease progression on or after platinum-based chemotherapy and at least one other prior line of therapy. Penpulimab is the second immune checkpoint inhibitor to be approved in the US for treatment of nasopharyngeal carcinoma;...

Many prescriptions for eye drops call for instillation of 1-2 drops. But Medical Letter consultants in ophthalmology seem to agree that all eye drops should generally be given in doses of only one drop. The volume of a single drop can vary with the viscosity of the solution, the design of the dropper, and patient technique. The average volume of a drop is 35-50 microliters, but can be as high as 75 microliters. An eye brimming with fluid holds 30 microliters at best, so even one drop is often an overdose. A second either washes out the first or increases the possibility of systemic toxicity,...

IV antiviral drug remdesivir (Veklury) has now been FDA-approved for treatment of COVID-19 in patients ≥28 days old who weigh ≥3 kg and are either hospitalized or at high risk for progression to severe disease. Remdesivir was already FDA-approved for these indications in patients ≥12 years old who weigh ≥40 kg; it was available under an Emergency Use Authorization (EUA) for younger or lighter patients. Remdesivir is the first drug to be FDA-approved for treatment of COVID-19 in children <12 years old.

The FDA has approved ceftolozane/tazobactam (Zerbaxa – Cubist), a combination of a new cephalosporin antibiotic and a beta-lactamase inhibitor, for intravenous treatment of complicated urinary tract and intra-abdominal infections in adults.

Eravacycline (Xerava – Tetraphase), a new synthetic tetracycline antibiotic, has been approved by the FDA for IV treatment of complicated intra-abdominal infections (cIAIs) in adults. Eravacycline is structurally similar to tigecycline (Tygacil, and generics), a broad-spectrum tetracycline approved by the FDA for IV treatment of complicated skin and skin structure infections, complicated intra-abdominal infections, and community-acquired pneumonia. A higher rate of mortality has been reported with use of tigecycline compared to other antibacterial drugs; it should be used only...