Rani Therapeutics, a start-up with a new way to turn injectable drugs like insulin into pills, has raised another $39 million, bringing its total cash haul to $100 million.

The pharmaceutical sector has long searched for ways to alleviate the $289 billion annual cost of patients that neglect to take their medication. Many of these patients will avoid needle-based injections in particular, as they can be scary, expensive and/or painful.

For that reason, the so-called "oral biologics" space presents a huge opportunity for life sciences start-ups, but it also comes with significant technological hurdles.

Rani's approach involves delivering an injection straight into the intestinal wall, which the company's CEO Mir Imran describes as "pain-free."

The company has devised a robotic pill that moves through the stomach, causing the outer case to dissolve in the small intestine.

A valve releases, fusing two previously separated chemicals to form carbon dioxide. That generates the necessary force to inject a needle-like structure made of sugar into the intestinal wall. That needle will then dissolve naturally, said Imran.

The company's technology is not currently used by patients, as it is still in the pre-clinical trials phase and has not yet been tested on humans.

Imran expects that the company will bring its technology to market in "two to three" years with an initial focus on diabetes, rheumatoid arthritis and other common, chronic conditions.

The new funding brings the company's total to $100 million. Current and existing investors include GV, Alphabet's ventures arm, as well as drug makers Novartis and Astra Zeneca.