S&P/ASX 300 Index (ASX: XKO) healthcare stock Immutep Ltd (ASX: IMM) is charging higher today.

Shares in the clinical-stage biotech company closed yesterday trading for 35.5 cents. In earlier trade, shares were changing hands for 38.5 cents apiece, up 8.5%. After some likely profit-taking, shares are currently trading for 37.7 cents each, up 6.2%.

For some context, the ASX 300 is up 0.4% at this same time.

This outperformance comes following the release of promising new clinical trial data.

Here's what we know.

What did the ASX 300 healthcare stock report?

Investors are bidding up the ASX 300 healthcare stock after the company announced positive clinical results from Cohort B of its TACTI-003 Phase IIb trial.

The trial is evaluating the efficacy of Immutep's Efti product used in combination with Merck & Co's Pembrolizumab in difficult-to-treat head and neck cancer patients with negative PD-L1 expression.

(Quite a mouthful, I know!)

Immutep noted that the latest data shows strong overall survival, progression-free survival, and durability from the novel combination of treatments.

The complete response rate increased to 12.9% and 16.1%, according to RECIST 1.1 and iRECIST, respectively.

ASX 300 investors also look to be reacting positively, with Immutep reporting that the median overall survival has not yet been reached, and the 12-month overall survival rate is 67%. Both were said to be "well above" historical controls.

The treatment was also continuing to be well tolerated among the patients in the trial.

What did management say?

Commenting on the trial results sending the ASX 300 healthcare stock soaring today, Martin Forster of the UCL Cancer Institute and University College London Hospital NHS Foundation Trust said:

The new survival and durability data, coupled with increasing complete responses, build on the strong response rates already established with this novel IO combination in head and neck squamous cell cancers with PD-L1 CPS.

Immutep CEO Marc Voigt added:

Despite the significant progress of cancer immunotherapy over the past decade and the positive change in the therapeutic landscape it has brought to bear, head and neck cancer patients with PD-L1 expression of less than one continue to have limited treatment options that all include chemotherapy.

We believe this data is an encouraging step in the right direction towards potentially bringing a new approach to this underserved population, representing up to 20% of patients with this difficult disease.

Looking to the next steps for the ASX 300 healthcare stock, the company said it will continue to follow the maturing data from the TACTI-003 trial while engaging with regulatory authorities for potential commercial paths forward.