LONDON, July 22 (Reuters) - AstraZeneca is casting its net wider in the hot cancer immunotherapy field through a clinical trial collaboration with U.S. biotech firm Advaxis that will test drugs from both companies in combination.

Britain-based AstraZeneca - the target of an unsuccessful $118 billion takeover bid by Pfizer earlier this year - is banking on widespread use of its immunotherapy drugs, which boost the body's immune system, to fight a range of tumours.

Under the deal with Advaxis, its so-called anti-PD-L1 drug MEDI4736 will be evaluated in a Phase I/II clinical study together with the U.S. company's cancer vaccine ADXS-HPV in patients with human papillomavirus (HPV)-associated cervical cancer and HPV-associated head and neck cancer.

Since the two medicines work in different ways, the hope is that combining them will produce a stronger response.

AstraZeneca is already running other combination trials using its own in-house products. Its MedImmune biotech unit also has a similar external collaboration with Incyte to study MEDI4736 with Incyte's drug INCB24360.

(Reporting by Ben Hirschler; editing by Jason Neely)