World Tuberculosis Day: TB Drugs Round-Up
LONDON, UK (GlobalData), 22 March 2013 - As World Tuberculosis Day approaches, GlobalData takes a look at the latest medical innovations in the fight against this deadly disease, which infects nearly nine million people annually.
Tuberculosis (TB) infection is a hot disease market for vaccine manufacturers, as the BCG vaccine, which has been the sole preventative TB treatment to date, does not produce a high enough level of seroconversion in all patients. This limits the intended effects of a vaccine, and increases the cases of pulmonary TB infection as a result of a poor immune response. The BCG vaccine also shows decreased immune responses several years post-vaccination, limiting the long-term effects of immunization.
Unfortunately, a recent highly anticipated trial of a TB vaccine yielded disappointing results. A recent study published in The Lancet on February 4th, 2013, showed that new vaccine, modified vaccinia Ankara virus-expressing antigen 85A (MVA85A), in HIV-negative infants who had received a Bacille Calmette-Guerin (BCG) vaccination, showed no statistically significant increase in protection against tuberculosis and Mycobacterium tuberculosis infection.
With the stagnated development of TB prophylactics, GlobalData's senior infectious disease analyst Dr. Ramya Kartikeyan expects that therapeutic regimes for TB sufferers will remain the only viable therapy option for the foreseeable future. Treatment regimens requiring shorter timespans and less frequent doses of medication would make an incredible difference to treatment adherence however, and recent trials have shown exciting progress in these respects.
A novel anti-TB drug cocktail of PA-824, moxifloxacin and pyrazinamide generated encouraging results in a recent Phase II trial in 2012, funded by the non-profit TB Alliance, demonstrating the ability to eliminate 99% of the Mycobacterium tuberculosis found in patients' sputum following only two weeks of treatment. This treatment could potentially offer a radical alternative to the six-month TB treatment regimens currently on the market, if the therapy progresses though this early clinical development, says Dr. Brad Tebbets, infectious disease analyst at GlobalData.
Preliminary results of a randomized, multicenter clinical trial, presented at CROI 2013, also demonstrated the successful replacement of daily doses of isoniazid and rifampin with higher weekly doses of Priftin (rifapentine) and Avelox (moxifloxacin) during the unsupervised continuation phase of treatment. As reported by Dr. Charalampos Valmas, infectious disease analyst at GlobalData, the results proved that this weekly schedule is non-inferior to the standard once-a-day treatment, with the greater dose of antimicrobials mitigating the high relapse rates that plagued previous endeavors to optimize the treatment schedule.
Finally, progress has also been seen in the fight against increasingly common drug-resistant TB cases, as December 2012 saw the FDA approve Johnson & Johnson's Sirturo (bedaquiline), the first new TB drug in decades, specifically for the treatment of multidrug resistant tuberculosis (MDR-TB), to be used in combination with other drugs used to treat TB. Kartikeyan says: "The approval of Sirturo is the first example of a successful accelerated approval since the instatement of the GAIN Act in the US. However, one begins to question whether the approval of Sirturo is likely to shift the balance in favor of therapies, instead of focusing on prophylactics in the case of rapidly mutating resistant bacterial strains. Furthermore, the recent sequestration cuts in the US and the financial austerity measures within the EU will put further strains on the regulatory authorities". Dr. Kartikeyan also opined that given the recent failure of a TB vaccine she was confident that the GAIN Act will serve as a band aid solution until vaccines are available.
"Developing countries will also benefit from point of care diagnostic assays and tests, which can help to direct effective treatment to patients at an earlier stage and thereby, limit the emergence of resistance".
Even once efficacious products are developed, pharmaceutical production can falter. Earlier this month, Sanofi's ($SNY) tuberculosis drug Rifamate, which combines the antibiotic rifampin with isoniazid, was put on the FDA shortage list due to manufacturing delays. The reason for this is not publically known, but the FDA states that Rifamate isn't expected to be available for patients until July. The Centers for Disease Control and Prevention says isoniazid and rifampin are the two most important treatments for TB, and so this pharmaceutical drought will be badly felt by TB sufferers. Sanofi were involved in another TB-related shortage last summer, when the company's vaccines unit pulled four batches of the TB vaccine BCG due to plant sterility problems.
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