August saw two major milestones for diagnosing and curing extensively drug-resistant tuberculosis, or XDR TB—the most drug-resistant of TB strains. On 14 August, the US drug regulator approved a new drug—Pretomanid—only the third new antibiotic developed to fight TB in over half a century. It’s a ray of hope for some 2,700 people living with the superbug in India, as per 2018 figures from the Revised National Tuberculosis Control Programme (RNTCP).
Pretomanid is promising, especially since, unlike the last two drugs—Bedaquiline and Delamanid—it is developed by the non-profit TB Alliance rather than a traditional pharma company. As The Ken has reported earlier, pharma companies prefer to control supply. TB Alliance, meanwhile, is all about access. US-based Mylan N.V. will bring Pretomanid to India after November 2020. While this is reason enough to hope that the drug will be available to those in need, the story is not the same for the second breakthrough that also came about in August.
On 8 August, six-year-old Bengaluru-based genomics company MedGenome announced it had developed India’s first Whole Genome Sequencing (WGS)-based test. Called ‘SPIT SEQ’, it provides a detailed analysis of every single mutation present in tuberculosis bacteria directly from a phlegm sample. Sequencing of the bacteria’s DNA can show the entire resistance profile of the patient, allowing doctors to determine every drug they are resistant to in one go.
SPIT SEQ is a marked improvement from the conventional culture growth test. Not only does it test for antibiotic resistance across a wider range of drugs—13 as opposed to 4—but it also brings down diagnosis time. Currently, patients must wait until testing on all possible drugs is done. With a long turnaround diagnosis time, repeated testing leads to multiple changes in the course of treatment. The whole process can take upwards of eight weeks—a criminal delay when time isn’t a luxury. Finally, after much trial and error, doctors settle on the right cocktail of drugs necessary for treatment. ‘SPIT SEQ’ cuts through this, enabling doctors to quickly prescribe the most effective drug to a tuberculosis patient within days.
SPIT SEQ is special because while WGS itself is common the world over, most of it is done using culture. This isn’t ideal because the TB bacteria (mycobacterium tuberculosis) takes upto eight weeks for culture growth. MedGenome, however, uses a microbacterial bait to isolate and extract the TB DNA directly from phlegm samples, speeding up the process while remaining accurate. At present, SPIT SEQ allows for diagnosis in less than 10 days, and has been validated with over 100 samples where it recorded 100% sensitivity and 98.04% specificity when compared with German company Hain Lifescience’s Line Probe Assay.
However, this leap in TB diagnostics has a catch.
