Should You Worry About What TG Therapeutics Inc (NASDAQ:TGTX) Has Just Done?

TG Therapeutics Inc (NASDAQ:TGTX) has unexpectedly altered the protocol for the GENUINE Phase 3 clinical trial of its lead drug candidate TG-1101. The compound is being developed as a potential treatment for relapsed high-risk chronic lymphocytic leukemia (CLL).

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The original study plan

As per the original plan, there were two parts to the Phase 3 study of TG-1101. Part 1 of the study was to test TG-1101 in combination of AbbVie Inc (NYSE:ABBV)’s approved CLL drug known Imbruvica. TG Therapeutics intended to enroll 200 patients in Part 1 study whose primary endpoint was to be the change in overall response rate (ORR).

On the other hand, Part 2 was to still test TG-1101 as a combination treatment with Imbruvica with the endpoint being progression-free survival (PFS).

The amended study plan

TG Therapeutics’ amendment of the study protocol for GENUINE Phase 3 trial of TG-1101 has affected Part 1 but completely eliminated Part 2. The effect on Part 1 is that instead of enrolling 200 patients, the study will now enroll 120 patients. Part 2 has been done away with and that could be the reason investors abandoned the stock immediately the news of the study protocol amendment entered the market.

FDA approval of the study amendment

TG Therapeutics said that the FDA has blessed its changes in GENUINE study plan, adding that the changes will enable it to seek accelerated approval of TG-1101 if the remaining Part 1 study is successful. Furthermore, TG Therapeutics said the amendment of the Phase 3 study plan would save it at least $10 million in costs related to the development of TG-1101 over the coming two years.

Patient enrollment

TG Therapeutics plans to complete enrollment for the GENUINE study by the end of 2016. Topline data from the study are expected in 1H2017, with application for approval targeted for early 2018.

Heightened approval risk

Despite TG Therapeutics’ soothing explanation of the change in GENUINE study protocol, investors seemed to worry that skirting progression-free survival test reduces the approval chances of TG-1101. The reasoning is that if Part 1 study that measures ORR didn’t pan out, maybe the Part 2 study, which was set to measure PFS, would save the day. Now it seems as TG Therapeutics has put all its eggs in one basket.

TG Therapeutics stock pulled back almost 17% to close the last session at $6.85.

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