Does the Catholic Church allow scientific experiments that deliberately inflict some degree of pain on a human being?

Discussing "indirect suicide", McHugh, O.P., & Callan, O.P., write in Moral Theology:

1857. Indirect Suicide.—Indirect suicide is committed when one is the cause of an act or omission, indifferent in itself, but from which one foresees as a result that one's life will be lost or notably shortened. This kind of "suicide" is lawful when and if the conditions for a case of double effect are present—in other words, if there is a proportionately grave reason for permitting the evil effect (see 103 sqq.). The following reasons are considered sufficient:
      
      (a) the public good, for the welfare of society is a greater good than the life of an individual. Eleazar is praised because he exposed himself to death in order to deliver his people (1 Mach. 6:43ff.). It is not sinful, then, but rather obligatory for a soldier to advance against the enemy or to blow up an enemy fortification, though it be certain that his own death will result; nor is it wrong for a pastor to go about ministering to his flock during a pestilence, though it be certain that he will fall a victim to the plague. Explorers and experimenters may also risk their lives for the advancement of science;

Does the Catholic Church allow scientific experiments that deliberately inflict some degree of pain on a human being?

Scientific experiments on human beings must maintain respect for dignity the human person. Scientific experiments for the sole reason of deliberately inflicting some degree of pain on a human being are forbidden. Certain moral rules do exist. Causing pain may be a secondary and unwilled side affect of scientific human experimentation and as such could possibly be morally permissible if Catholic moral criteria are upheld.

The Catechism of the Catholic Church says the following:

Respect for the person and scientific research

2292 Scientific, medical, or psychological experiments on human individuals or groups can contribute to healing the sick and the advancement of public health.

2293 Basic scientific research, as well as applied research, is a significant expression of man's dominion over creation. Science and technology are precious resources when placed at the service of man and promote his integral development for the benefit of all. By themselves however they cannot disclose the meaning of existence and of human progress. Science and technology are ordered to man, from whom they take their origin and development; hence they find in the person and in his moral values both evidence of their purpose and awareness of their limits.

2294 It is an illusion to claim moral neutrality in scientific research and its applications. On the other hand, guiding principles cannot be inferred from simple technical efficiency, or from the usefulness accruing to some at the expense of others or, even worse, from prevailing ideologies. Science and technology by their very nature require unconditional respect for fundamental moral criteria. They must be at the service of the human person, of his inalienable rights, of his true and integral good, in conformity with the plan and the will of God.

2295 Research or experimentation on the human being cannot legitimate acts that are in themselves contrary to the dignity of persons and to the moral law. The subjects' potential consent does not justify such acts. Experimentation on human beings is not morally legitimate if it exposes the subject's life or physical and psychological integrity to disproportionate or avoidable risks. Experimentation on human beings does not conform to the dignity of the person if it takes place without the informed consent of the subject or those who legitimately speak for him.

2296 Organ transplants are in conformity with the moral law if the physical and psychological dangers and risks to the donor are proportionate to the good sought for the recipient. Organ donation after death is a noble and meritorious act and is to be encouraged as a expression of generous solidarity. It is not morally acceptable if the donor or his proxy has not given explicit consent. Moreover, it is not morally admissible to bring about the disabling mutilation or death of a human being, even in order to delay the death of other persons.