When the strongest antibiotics stop working
Carbapenems are some of the most powerful antibiotics doctors have. They're often saved for the worst infections, when other drugs have already failed.
But over the last decade, certain hospital bacteria have learned to defeat carbapenems too. When that happens, options narrow fast.
A new clinical study tests an intravenous version of an old drug as one possible answer.
Carbapenem-resistant infections are among the most urgent threats in modern hospitals. The bacteria can cause pneumonia, bloodstream infections, and severe wound infections. Mortality rates are high — sometimes one in three patients — partly because there are so few drugs left that work.
The pharmaceutical pipeline for new antibiotics has slowed for years. Reformulating older drugs that still work against resistant bacteria is one of the more practical near-term strategies.
That's the idea behind BV100.
The old way versus the new way
Rifabutin has been used for decades, mostly in oral form, to treat tuberculosis and certain other infections. It works against some carbapenem-resistant bacteria, but the oral version doesn't reach high enough blood levels quickly to handle severe, fast-moving infections.
BV100 changes that by delivering rifabutin intravenously. Doctors can get high blood concentrations within hours and adjust the dose in real time — exactly what's needed when a patient is critically ill.
The Phase 1 trial reported here is the first careful look at how the IV version behaves in healthy people.
Imagine trying to put out a fast-moving fire by sprinkling water from a watering can. The water reaches the flames, but slowly. A fire hose delivers the same water with much more force and timing.
Oral rifabutin is the watering can. BV100 is the fire hose. Same active medicine, very different delivery. The IV route lets doctors control exactly how much drug a patient gets and how quickly. That control is critical when bacteria are doubling every 30 minutes.
The study snapshot
The team ran two complementary trials. One tested single ascending doses — giving healthy volunteers one dose at increasing strengths to see how the body handles it. The other tested multiple ascending doses, where the same volunteers received the drug repeatedly over several days at different intervals. Blood samples tracked drug concentration and broke down how the body processed it. Volunteers were also closely monitored for side effects.
BV100 behaved predictably. As doses went up, blood levels rose proportionally. The drug stayed in the system long enough to support either once-daily or twice-daily dosing, and twice-daily dosing produced the higher overall exposure expected from any drug given more often.
The medicine's main breakdown product made up less than 5% of total activity, suggesting it doesn't significantly add to either effectiveness or risk.
Side effects were what doctors would have predicted from rifabutin's long history. The most common issue was reactions at the infusion site, more frequent at higher doses and longer infusion times. No new safety problems came up.
Based on these results, doses of 200 to 300 mg every 12 hours have moved into Phase 2 testing in patients with actual carbapenem-resistant infections.
This was a healthy-volunteer study, not a trial showing patients got better.
Where this fits in the bigger picture
Drug-resistant infections kill more than a million people worldwide each year. Most new antibiotic candidates either fail in trials or take a decade to reach patients. Reformulating drugs that already work — like rifabutin — offers a faster way to expand the toolkit.
If BV100 holds up in the next phase of testing, it joins a small but important group of newer agents available for the hardest hospital infections.
If you or a family member ends up hospitalized with a serious infection, you don't need to know the name of any specific drug. Hospital infectious-disease teams choose antibiotics based on the bacteria identified and what's known to still work against them.
The bigger takeaway is for everyone. Antibiotic resistance is a slow-moving emergency. Using antibiotics only when truly needed — not for every cold or sore throat — helps preserve the ones we still have, including the next generation in development.
Phase 1 trials are designed to test safety, not whether the drug actually cures infections. The participants here were healthy adults, not critically ill patients with resistant bacteria. Real-world dosing may need to be different in patients with kidney or liver problems, or those taking other medications. The infusion-site reactions also need to be looked at carefully in sicker patients.
A Phase 2 trial is now testing BV100 at the recommended doses in patients with carbapenem-resistant infections. That study will measure both safety and clinical response. If the results are encouraging, larger trials will follow. The whole process typically takes several years before a drug becomes widely available — but the urgent need for new options against resistant infections is keeping the pace moving.